Struggling, When is the right time Options

[Sillybeans]

My sweet 18 year old baby has CRF. I thought we had it under control with the sub q fluids and the special food, but I'm watching her go down each day. She is still moving about and drinking and using the bathroom, but she refuses to eat anything offered. Her weight has gone from 11 to 5 lbs and she vomits several times a day. I can't tell if she is in pain. I don't want her to suffer. I want to fix what's wrong but I don't know how. She has medication for appetite but will throw it up right after getting it. It's hard for me to seperate and judge her quality of life. I'm not ready to give up and let her go, but I never NEVER want her to suffer. How do I know? When is it time?

[Sillybeans]

We have the results from my vet consultation. It's a mix of good and bad. I'll start with the weight. The last weight taken was the weight I gave on my original post. It was incorrect. The nurse subtracted the weight of her carrier, but she was weighed out of it. Her weight is 6.89 lbs.. Her heaviest has ever been 11 lbs.. While this is not good, we have figured out some possible causes. She is still suffering from a UTI that she had in December. It seems the course of antibiotics she was given should have been longer than 7 days. We are now on a 14 day course as well as receiving an antibiotic shot. Also, the perscription food she was on did not agree with her. Her food was changed to another brand which she seems to enjoy and keep down in small amounts. He added a little Zantac in for nausea and good measure. He said she looked alert and feisty.
The bad:
Her values were higher. He said we can try these things ( antibiotics, food, Zantac) and see where we are in a month, but that it is possible the vomiting will continue due to toxins.
He said he believes she has time left with us and that he believes she was feeling bad due to the UTI.
Of course I am happy, but I'm trying not to get my hopes up. I still feel that dread in my heart.
Thank you all so much for listening and understanding. All thoughts and opinions are welcome.