Older roommate (blonde) is my thing, and yours is on point, which is hot body, confident look, short clothes and without anything over the top like extremely huge boobs. You don't have to change anything about her, trust me.
Maybe just give her a job or her own thing she works at, making her the "one with a future" between the 3 "roommates".
The brunette roommate looks odd/nerdy in the first renders, probably because of the clothing and face.
BUT, on the next renders you posted, I understood her vibe, and can even say I like her.
I personally wouldn't mind if she looked nerdy at the start of the game, but then you accidentally see her naked and think "who is that? It can't be her!", and after that she starts wearing better clothing and being more confident.
I can't say anything about the mo... I mean, landlady cause I always ignore that character in this kind of games, as I personally have no interest on that, although I know people love it.
Overall, your project looks good, I'd love to see it going