Replying to Odds, 1 in a Million?

So there was this girl the other day in my class in college, asking if anyone wanted to have a free cat, A grey tabby longhaired cat, I mentioned that my I'd have to ask my parents, to see if they'ed want to take on another pet, As it turns out they said No, because our other cat is in her old age, and it would only create problems.

The girls sister was getting rid of the cat because she couldn't clean the Kitty litter, because she's pregnant.

Now there has been a stray grey cat around my house, & my Neighbors house lately, a house broken, people friendly cat, Longfurred, I feed the cat just now, and it was ravenously hungry, and looked like it's been a while since it had food,

My Question, Is what do I do with this Girl i take class with, tell her? Or ask where they dropped off the cat, Or if she looked my house up, and dropped it off on my doorstep leaving food, Honestly like what the fuck?

I almost want to phone the SPCA and rat out my class mates sister, (IF that would actually do anything) but the other thing I don't want to do is confront my classmate over the issue, because I think it would create resentments, we are a small group in the class who have to work together daily on practical assignments,

The other funny thing is the girl doesn't live on this side of the city, what are the odds?

Just like those girls on the Montel show, I'm 100% sure that it's my classmates "Baby" (Cat)