So very sorry to hear about Tiffy xxx
Sense of smell can be reduced due to a build up of uraemic toxins, some times it helps to heat food a little to encourage them to eat. There are actually quite a lot of things you may be able to try to encourage Tiffy to eat.
Have you looked at the CRF site?
http://www.felinecrf.org/index.htmIts a very large site but packed full of very usefull info, for the time being though, pick out the bits that are more important to you and Tiffy at this point in time.
You may also want to try some slippery elm bark along with her food, either and hour or so before or after medications. This would help with any mouth ulcers as well as nausea.
Try raising her bowls too so that she doesnt have to lower her head too much whilst eating or drinking, this too may help with any tummy acid problems.
You may also want to add B vitamins to her food and water. B vitamins are water soluble, therefore any excess will be flushed out of her system via urination.
All these things and more are what i used to do for my old boy. He was diagnosed at the age of 18 and a half and went on till he was 21. There were times I thought he was nearing the end but would then bounce back just as quick so please try not to despair too much just yet.
The important thing for Tiffy right now is to get her eating again. Would she be tempted by some smelly fish such as sardines? I know its not on the vets menu for CRF but it may get her eating again.
It may also be worth looking into getting some Iron and B vitamins, I used to buy this in the form of Pet tinic and found it invaluable. It does have to be ordered from the USA but if you would like I could ask around and see if I can get some for you sooner. Infact I think DD has a bottle which she may be able to send you.
I hope some of that helps a little, if I can think of anything else I'll get back to you. There are also others here that have alot of experience of CRF that may be able to help too.
I wish you and Tiffy all the very best and send you both lots of love and well wishes. xxx