Hi Scotcat, I agree it sounds like dementia especially at 20! Steroids are anti inflammatories but also perk them up, make them feel euphoric and mask what is really wrong with them (no harm in that if they feel better imho) and are better tolerated by cats than dogs. I wouldn't worry about her taking them and no, they don't just give them before having a cat pts so please don't think that. I've read on the NOAH drugs website that it's possibly better to give cats their steroids at night if possible - something to do with their night time production by their adrenal glands so it's better then. If her blood pressure is high she could be crying too - did the vet take it? Old cats often have high bp.
My Swampy's been off and on Vivitonin, which is actually a drug; you give about 1/4 tablet (teeny) and it increases the supply of blood to the brain. The vet explained to me that with dementia not enough blood is going through their brains. It can perk them up too. I've used it with Swampy, with mixed results. He became less confused, but I think a little more agitated. He is now on a trial of Selgian, an anti depressant of the anti histamine (calming) type as FABcats publish a paper on their website suggesting good results with it with dementia and dementia-type agitation. They also mention vivitonin as having had some success btw. If I hear any more about it, I'll post. The link I put on Swampy's thread to messybeast.com explains really well about senile dementia behaviour in cats.
Try not to worry and a big hug to Holly and you