Hello, Shamie and welcome.
I'm so sorry to hear that Abby is not in good shape after her 'adventure.'
If she is eating and drinking, that's a very good sign, but she definitely needs to be evaluated in person by a vet, to see if she has any external or internal injuries and perhaps be given antibiotics, if she has contracted any infections. They should also do basic blood work.
I'm assuming she's vaccinated and up to date on all her shots. If not, the vet will need to vaccinate her, but most likely want to wait until she's stronger, as she can have an allergic reaction to some vaccinations and if she's in poor health now, she needs to build herself up, with your help and TLC, of course.
If she is eating and drinking (just give her small amounts of food at one time, so she doesn't gorge and make herself sick and also monitor her water intake and don't let her drink too much at one time), plus, using the litterbox normally (when she has enough food and fluid in her), a recovery does seem possible; however, right now, you need to check her over for any external wounds like scratches, bites, any bumps or lumps that may be abscessed wounds. Also, check her for external parasites, like fleas or mites. If she was outside for any length of time, having fleas or mites is very possible/probable. This would need to be treated with a topical flea treatment like Advantage or any one sold by your vet, but again, it's not recommended to apply this treatment to sick or debilitated cats, so you might have to wait a little bit longer, to see how she's recovering. If she does have a bad flea infestation, there is an oral remedy called Capstar which is available online or at pet stores.
Check the color of her gums to see if they are light pink and moist. If they are paler than light pink, like white, this is a symptom of anemia and if they are not moist, but tacky, this is a symptom of dehydration and she will need to be seen by an ER vet center, tonight. It will increase her chances for recovery if she can be given I.V. fluids and any medications, if necessary.
If she were mine, I'd try my best to have her seen by an ER vet now, if your vet doesn't have emergency hours.
I hope Abby will recover well, and I know you will take all precautions to never allow her to get outside again.
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