Two young girls living in NYC, go to private school, live in modern high-rise. One is white, one is asian, reminds me of Eloise stories, but for slightly older kids. I remember they loved getting dressed up in their mother’s evening gowns and drinking seltzer out of martini glasses.
Lost Classics of Teen Lit: Name That Book! 
The book was primarily set in a facility, where the protagonist and her caregiver, a felinid of some sort, lived. The facility provided for their needs, and there was another being of the caregiver’s species there, though there was implied friction between the two. The protagonist had memories, very faintly, of another person like her, and eventually she met with the person from her memories, a boy, who was in the care of the other person of her caretaker’s species. The caregivers’ species experienced time as a series of rooms, where entering one made the doors to other times close, and the boy and girl eventually came together, fell in love, and explored outside the facility, finding that the rest of the world was basically an apocalypse, only to eventually reunite with their caregivers, who left to rejoin their species and the last surviving humans outside of the facility. I remember that the humans had cryogenically stored embryos, and the girl’s had simply been left, with her parents not wanting her after all. and that the caregivers’ people called themselves by a cat-sound. the surviving human who came to talk to the girl and the boy had yellow eyes, too.
I read this book sometime around 2003-2004, and the book was already kind of old by then.
The cover aesthetics were very 1970s/early 1980s, almost giving Star Wars and Tatooine vibes.
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