Maybe she’s not that kind of girl who talks that much about herself, which includes her boyfriend. But you could just see what she says if you make her compliments or such, if she says things like that to you too, gives you compliments back, how she reacts in general. Or just go straight ahead and tell her. If you’re talking for a while now there might be a chance that she likes you too.
You can also write me off anon so we may talk, if you need any help/advice/love
It’s definitely possible I can tell but being completely honest I don’t know if it’s “okay”, I’d say it depends on how far you’re going, how much you’re into that other person.