I'm a cat lover too so I would never call you a crazy cat lady, OP.

I get it.
My only concern is this - if you separate your original kitty from the other two cats (or even just the other cat who is also "officially" yours), will that be difficult for her? It sounds like the three cats have been together a long time.
Also, cats are very sensitive to their environment and take a long time to adapt to a new home; going back and forth from your old house to your mom's house to your new apartment...that's a lot of change
So do take all of that into consideration. What does your mom say about all if this? IS she willing to keep all three cats as her own, permanently? If they're happy and settled there, that might not be a bad idea. But just taking the one cat and making her adjust to a brand new apartment AND a new cat (who may already be territorial in your home), could be tricky.