Its an old one-like 80's or 90's based on the curly hair of the female MC and the fashion.
The main MC has a thing for rich guys, and kind of changes her personality to get with and maintain a relationship with them.

The first boyfriend in college is preppy and rich, and he has a best friend who is kind of vulgar- he smokes, drinks, gambles, and is CONSTANTLY arguing with the MC behind her boyfriends back because he knows she's phony.

I think it then skips ahead and she's dating some other rich guy or is engaged, and she runs into the oldest friend of her ex at a horse racing event. He again kinda calls her out on her gold digging ways, and basically tells her that she needs someone that she can fight/argue with.

I think they end up going to a pachinko place and spend all day together? And have fun? And I think they end up together, eventually? At some point I think she ends up dating someone she meets in a library who's a bit older but he ends it with her?

Any help😕