hi Rita!
The very first cat I ever owned (only about 8 years ago now) was a stray. I decided to keep him for sure so I took him to the vet and I was so happy because I had made the decision (I had wrestled with it prior to my trip to the vet) but the vet came back into the room and said "oh I am so sorry, your little guy does test positive for leukemia"---wow! here I decided to own a cat for the first time ever and it has leukemia!!?? bummer!! so I sadly said--"ok then I guess you should put him to sleep or something, right?"--"nope" he said, "with proper nutrition he might live almost as long as a regular cat--!"
So I took him home and never let him go outside where he could get into anymore trouble..named him Viktor and he was my pride and joy for 6 years. (I have no idea how old he was when I got him) I really wish it could have been longer!! After all that vet had said almost as long as a regular cat so I was counting on 10 years. darnit. But one neat thing was that everyone told me that the end might be "horrible"...in our case it wasn't. He just stopped wanting his food. Sometimes a cat with leukemia will start to get very sick and throw up all over the place (sorry to be so graphic) but Viktor didn't do that. He just really lost his appetite. When he would not eat I took him to the vet and the vet did tests that showed he was so anemic there was no recovery possible. So we did the responsible thing and had him put to sleep. I cried for one week solid. But I also had 6 of the best years with the neatest cat. He loved to play all the way to the end.
He lived as long as he did because we gave him spendy nutritious food ..you know the science diet stuff and also max cat and vitamins too. It was so hard to lose him. But he introduced me to cats in general--previously I was a "dog person".
Sometimes I think Felv cats can go into a REALLY dramatic remission--(and later test negative) you can hope for that too. Just know that plenty of people have been in your shoes. Your cat's life is going to be abbreviated to some degree. But you can still enjoy eachother and she can do really well--just like my vet said "almost like a regular cat" (without problems) --actually no one ever knew Viktor had any health problems at all--all the way up to the end he was very beautiful.
good luck and let us know how you feel and what your plans are

there actually might be a google group with more information. I will check for you.
Patti