Feline Leukemia exposure

A very concerning cat situation has just popped up. My friend and I found a little cat about one year ago. We took her straight to the vet, she tested negative for felv and FIV, got all her vaccinations and a good check-up. She was pregnant. A week or so later, she had some secretions, and when she went back to the vet, the vet said she was re-absorbing the kittens, and seemed to have an infection. She got an emergency spay. My friend adopted her, brought her home, and she was doing great. Over the course of the next year, my friend adopted 2 other mommy cats in need. The second cat, Luna had 3 kittens. We found a home for two, and I kept one (my first cat ever). The third cat is named Lucy. About 2 months ago, she took in one foster, Cabbage. For a total of 4 cats. All of the cats were fully vaccinated and tested before being added to her home (gradually, as prescribed). About a month ago, we noticed that Lily, the very first cat, would smell and occasionally touch her tongue to the clay litter. She called the vet, and she said it was probably nothing to worry about, just keep an eye on her. A few weeks later, Lily was spotted licking a clay flower pot a couple of times. We suspected anemia. My friend had also recently switched her cats to a new food (about 2 months ago), Wellness core, which is really high protein, and is supposed to help cats stay at a healthy, lean weight. Well, since the switch Lily had lost about a lb. My friend wasn't sure whether to be worried, but already had a vet appointment about the flower pot licking. At the appt, they did a blood panel. The results came back today, with elevated protein and anemia. They brought her back in today and she tested positive for Feline Leukemia. Apparently the first test was a false negative. It seems that she was possibly infected shortly before we had her tested the first time, and it wasn't showing up yet. In hindsight, maybe that could be why she aborted the kittens. In any case, she is heartbroken and panicked for the other 3 cats that have been living with Lily for months. I am also wondering how concerned I should be. The kitten that I kept from rescue mama #2, has been over to their house probably about 10 times, and even spent the night on a couple occasions when I was away. Should I be freaking out?

Thanks so much for the reassurances. The vet who has always seen Lily advised my friend that if it were her cat, she would go ahead and euthanize. Lily's bloodwork came back so wonky that she would have needed to start blood transfusions to prolong her life. She felt like she was on the slippery slope where she probably wasn't feeling great, and would soon start to really decline and feel horrible. Of course my friend and her boyfriend are heartbroken. Their other 3 cats tested negative yesterday, so they will get retested in a few months, but it looks like they are in the clear. My Iggy will be tested tomorrow, but I am feeling fairly good about it.

He tested negative, which is a huge relief!