how do i remember little details about people? i feel like an idiot

i guess the obvious reason i would forget certain details is because i wasn’t actually that interested in them in the first place? but that’s not how i feel. and it’s hard to explain that to people. for instance i’ve been talking to this girl who’s a senior in college, and i said something that made it clear that i forgot she was going to med school after. she told me i was fake and i just felt a huge wash of shame and guilt. then she asked me her favorite color and i didn’t know. then she told me mine and a couple of other random details including things i barely even remember saying. i just felt a pit in my stomach because this has happened before and i feel more horrible about it than ever because im actually being called out on it. i don’t think i could successfully explain to her that i was truly interested and i think she’s gonna just think im putting on a facade during conversation. is it more likely that deep down im really not that interested in these details and am subconsciously putting on a show? part of me feels like i just have bad memory because i forget a lot of things. should i write these things down in a journal or is that too weird? or is it “fake” of me to even actively try to remember these things just to seem more interested? am i overthinking? i feel so stupid this keeps happening.