
Hi Peanut
So sorry to hear this. One thing to beware of is that if a dog has been on prednisolone long term, they cannot stop taking it entirely, since the body has long ago given up producing any steroid of it's own, and it does need a certain amount to function. This is usually produced by the adrenal gland, but pred given over a long time convinces the adrenal gland not to produce it at all any more. I didn't really want to add to your woes, but please check this out with the vet. It might be that they plan to put her back on the pred instantly after the blood test, but do please check.
Don't know about milk thistle, but I have had very good responses from natural remedies, and usually they don't interfere with anything else.
I really hope that you find a solution to keep everything under control, don't give up - google everything like mad, there might be something out there to help. I will be thinking good thoughts for you both.