Hello and welcome.
First of all - although you haven't said how long it is since she stopped taking them, if she came off steroids in less than 12 months this is almost certainly a return of the PMR symptoms. Past experience has shown that about 25% do manage to discontinue pred within that sort of period - but remain at a higher risk of a relapse later. The pred doesn't cure the underlying autoimmune disease that gives rise to the symptoms. They allow you to manage you symptoms to allow a decent quality of life.
Secondly - it concerns me that you mention jaw discomfort as that is a symptom of giant cell arteritis - where there is a risk of loss of vision and high dosed pred is the only option, is associated with PMR and you are at a higher risk of developing it if you have PMR, more so if it is untreated.
I'm not sure we are allowed to name people but I can tell you that the biggest research groups are in Southend and Bristol. Follow this link to the top of this forum and you will find a link to a paper about the diagnosis and treatment of PMR and GCA from the Bristol group as well as a support site.
https://patient.info/forums/discuss/pmr-gca-and-other-website-addresses-35316
In response to your other points, I think you are being over optimistic but I'll do my best.
There is no way to 100% diagnose PMR - it is a diagnosis of exclusion and - as you can see from the Quick and Kirwan paper - the response to 15mg of pred can be used to differentiate patients with simple PMR (as opposed to secondary to something else which is also a possibility).
There are few options with regard to corticosteroid. Which you use depends on the length of effect you want and how it is to be used longterm. In PMR the choice is prednisolone in the UK as its effect lasts 12-36 hours (varies with person) and for most people a single daily dose works well. Other corticosteroids have a shorter halflife of effect so have to be taken more frequently.
It comes as simple cheapish white tablets or as more expensive enteric coated pills - they have advantages and disadvantages but both are used. I tried both, there was no difference in anything but I didn't have much in the way of sideeffects, more transfer of weight than weight gain! I have also had Medrol (methyl prednisolone) after I moved here to Italy - didn't suit me at all and the side effects I had were most unpleasant - but it is the standard here and it seems few patients have problems like I did. I am now on Lodotra, a form of prednisone (the difference is prednisolone is the active form, prednisone has to be processed by the liver to become active) which has been approved for use for morning stiffness in rheumatoid arthritis. It has a special outer coating, you take it at 10pm and it is released in the early morning after a 4 hour delay. A trial is being done to see if it achieves anything in PMR, it is already commonly used in its home country of Germany. Personally I think it is brilliant. However, the bottom line is, as you might expect, that it is expensive. Plain pred probably costs the NHS a few quid a month, Lodotra costs from £25 to £75 depending on the dose you are on - you can't cut the tablets so you have to combine 5, 2 and 1 mg tablets to get the dose as you reduce. The only times it is £25 is when you are on 5, 2 or 1mg - the rest of the time it is £50 or £75. Not expensive if you get a better QOL I suppose - but if every patient in the UK on pred was given Lodotra it would add a lot to the practice drug budget.
So no - no option to trial unless you can persuade your doctor to provide enteric coated, Medol or Lodotra or you are happy to pay for it yourself. The basic effect is the same. It is some form of prednisolone she needs.
"Draw up a plan to help her life with condition" - that is a bit naive if you don't mind me saying so. Unfortunately, no consultant has the time to spend with every patient to discuss that, unless you are paying through the nose for a private session and even then we know of people who went privately and had less friendly or polite treatment than from over-worked NHS people. How to live with PMR is firstly to take the pred and find the optimal dose by reducing VERY slowly to find the lowest dose that manages the symptoms to an acceptable level, secondly to arm yourself with reliable information from forums like this one and the other links you will find in the link I gave you and, if there is one, to join a support group to find out from others how they deal with it. Of course you didn't get those answers from a consultant - they've mostly never had it themselves and how you live day to day is less their job than identifying you haven't got something far more serious. There are some who believe once you are taking pred "everything is back to normal" - which isn't true in many cases.
If that sounds harsh or unsympathetic I'm sorry - but PMR is not life-threatening or life-shortening. It is life-altering to use the modern term but I don't imagine my grandfather and great aunt who almost certainly had PMR expected or even got pred to deal with their "rheumatics" - in those days it was accepted as part of growing old. By over 75 something like half of people have PMR. I have had PMR since I was 51, over 9 years. For the first 5 years it wasn't diagnosed, I didn't tick the boxes, I was "too young" and my bloods were "normal". When it suddenly got far worse it was the same - I found the diagnosis but the rheumy didn't believe me or listen to my story of the 70+% improvement in symptoms 6 hours after taking my first pred dose. The GP was happy to accept the evidence and I've been on some form of pred ever since, nearly 5 years. There are things I can't manage but frankly, at 61, I know a lot of others who are worse off than me. Most of the time I have continued to ski - not as much or as hard as some neighbours and not at all last year - but that was something else. I'm intent on going this year. At present I feel better than I have for several years - on 6mg/day pred. If that's what it takes - that's fine. My bone density is the same as it was 4 years ago pre-pred. I've lost weight, now I can move and walk a few miles without feeling I am dying of exhaustion. I restrict the housework I do - sometimes I get someone in to do a bit - and I started to cook differently so I didn't spend hours standing.
You can't "rid yourself" of it. It is an autoimmune condition and it may go into remission sooner or later, it probably does for most people, all you can do until then is modify your lifestyle to accommodate the problems and keep taking the pred. And it is a case of god helping those who help themselves. I've given you links for the PMR and GCA northeast support site and the associated forum. The site has medical and other information - all checked and monitored by experts including medics. That, I suppose is what you want but it won't come directly from the horses mouth - the site speaks for them. The forum is a gathering of people with personal experience who have advice and tips and sympathy on offer for you to take advantage of. Social media can be a wonderful thing.
We frequently have people say they have learnt more from us than from their doctors - but we have all walked the walk and have time and expertise to help you. With that knowledge you have the power to help yourselves and live as well as possible. There is no simple answer - each of us is different both in our PMR and also in how we respond to the treatment. The cause is an autoimmune disorder - no one knows why or how it works just how to cope with medication - but then it is up to us.
I hope this has helped you understand the source of your frustration - and I have pointed you towards help. I (and others) will happily try to answer your questions if you still have any after doing your homework and reading what is already on offer on the northeast site (you will!). If you visit the forum there you will also find some info about support groups - there is an excellent one which meets in Chertsey and is run by MrsO who also posts on here so I'm sure she'll provide information about that.
Keep in touch now you have found us - we'll do our best to guide you on your first steps in this new lifestyle. It needn't affect thing too much - as long as you moderate your expectations. Climbing Kilimanjaro will have to be postponed for now
Eileen