girl crush?!

hello! so i recently have been feeling like i have a crush on my friend who is a girl. this is like kind of my first time crushing on a girl but i think i've recognized it other times and suppressed it. the problem is i just recently was crushing on a guy who i was not super interested in emotionally but who would make me really horny just from being in close proximity to him and this situation is kind of the opposite. i really like my friend and could see myself doing things with her but i don't get noticeably horny just when we're hanging out or when she hugs me or anything. i've never had sexual experiences with either guys or girls (and i'm 20) so i'm just like confused. i don't know whether this is a red flag or not. do you usually get horny around someone you want to date or fuck, or is it usually if they do something that starts you off?