Flatmate got a cat when I wasn't home because I was grieving my dead baby

For context, I live in a city which is quite a distance from my hometown. I'd taken my cat to my hometown where she passed. I got back yesterday and I've just spent a lot of time being pissed off for the past few days because my flatmate decided to keep a cat when I wasn't home. I was back home, in my hometown, where I'd just lost my cat and spent a month and a half grieving my child. This person didn't even have the decency to tell me she'd kept a cat - aside from the fact that you're supposed to tell people you live with that you're adopting a cat, my soul cat, my sweetest baby had just died and I had no idea this was happening and only found out after my partner had gone to pick up my baby's things from the house. Anyway, the problem is- the person who dropped off this cat in the apartment is someone the flatmate and I both know and had gotten this cat with the intention of giving her to me because she was one of the first people I called after I found out about my cat. She wanted to help but I told her to take her back since I wasn't there and can't adopt a pet so soon and she said she'll take her back with her. So I thought that's where the conversation ended. But I came back yesterday and there was a cat in the house... and the connection was instant. She's been cuddling with me and slept in my arms last night. It's very strange, I have been having doubts because I keep feeling I'm disrespecting my Peanut, that I could just replace her like that. It's not the same, this new baby is not like her or her but I don't know... For the first time in weeks I felt like I could finally put the love I have for her somewhere. I did cry because this was the first time I came back to this house after my baby died, and now there was a random cat in my house and I was dreading coming back because this was her house- she came in through a window once and then never left. But yeah, it's still strange, to hold such enormous grief and the anticipation to love some thing with as much devotion as I loved my baby peanut. Anyway, I plan to talk to my flatmate about taking her when I leave. Apart from the massive inconsideration, I found a broken chicken bone in her food bowl and a messy, unclean litter box. I do suspect that she hasn't even been dewormed or vaccinated. I do feel slightly weird because she's named her? But I don't know.