Eh, I would think this fits 2nd degree murder - it’s a reckless disregard for human life to fire a gun in someone else’s apartment. Manslaughter usually involves crimes of passion or negligence.
But she thought she was in her own apartment. That is negligent homicide, i.e. manslaughter.
We live in a crazy world. A few years ago Mary Winkler murdered her husband with a shotgun while he slept. Clearly premeditated murder (even though people on here defended her because the perp was a woman and her victim a white man, so obviously lower on the progressive stack), but she was only convicted of manslaughter and had to serve mere 60 days. How is that manslaughter but this is murder?
Improper self defense is normally manslaughter.