Is she an orphan? Or it was never explained why she lives with her uncle? Just curious

I don't think it's ever been explained but her parents probably died a long time ago because she has been living with her uncle since she was a small child

I actually feel like she has absent parents, mostly basing it on the one chapter where she announces "I'm home... Not like anyone cares", which suggests to me that she doesn't live with her uncle because he definitely cares about her so much and she knows it. Also, the fact that at one point he even considered leaving means that he can't be her only family since, y'know, you can't just leave a 7 year old all alone (but he did have some doubts because it's pretty clear that he's the closest to her at least emotionally). So yeah, that's my take.

now that I've read your theory it really does make sense but maybe the author just didn't think about it to that extent ┑(￣Д ￣)┍

Yeah, that's definitely possible lol