she probably has worms which is why her stomach feels like its full. That comes with pretty much all feral cats. I would get an eye dropper and try to get some fluid in her that way. Try adding pedialyte to wetfood, water, or formula to help her stay hydrated. I will add a pedialyte tag which will show some other threads with similar problems. There should be some recipes for homemade pedialyte, if you can’t get it in a store. Leave a bowl of water or formula on the floor. She will get curious or step in it, or get it on her nose and lick it off. She will understand she is supposed to use her tongue eventually. Give her more diluted formulas so she starts getting weaned off the taste of milk and gets used to the taste of water. You can also mix a little gravy from wetfood in the bottle so she tastes that too. Diarrhea is pretty common in kittens. If pedialyte doesn’t work you can get canned pumpkin, not pumpkin pie filling mind you, and puree it and add it to her formula. Canned pumpkin does wonders for diarrhea, and should help her get more fiber in her body. If the diarrhea persists or she becomes lethargic or dehydrated, she should be taken into the vet to get fluids injected under the skin. Sometimes abandoned kittens have systems that shut down and it makes it hard for them to digest. As long as she is eating and not dehydrated, it is probably just because she went from mothers milk to formula. To recap:
Dilute the formula with more water and add pedialyte, if that doesn’t help,
add puree’d canned pumpkin to her formula or food
If diarrhea persists after 2 days or so, she should go in to see the vet
She can stay on the bottle a little longer if she is malnourished. But by 8 weeks she should at least be eating wetfood, even if she still drinks formula. Hope this helped at least a little!