Crush on senior

Okay so I'm a 20F med student and I have a senior in my college who I have a major crush on. By major I mean ✨MAJOR✨ Let's call her 'Z' Well I hated Z earlier coz I had a crush on 'O' back then and O liked Z. So I had this jealousy factor with Z and dayum can't deny but O has a gud eye. Idk how but I just started crushing over her, and my feelings for O just went off like wind.

But then, Z sees me as a friendly gud junior who asks her for tips and stuff, well atleast that's what I think she thinks abt me. I sincerely hope tht I'm wrong coz I want her to see me as a cute bi junior who steals glances at her and blushes whenever we have an eye contact.

Also, I'm scared to lose her and I want her to know that I like her before she starts dating anyone. I don't want to regret not confessing to her when I had a chance. But how do I do this? I've been rejected the only time I've confessed earlier to someone plus Z has already rejected O when she confessed.

So what I think is, if Z can reject O, I definitely do not stand a chance and might end up heartbroken so I shld just continue this silly crush thingy but at the same time I don't wanna regret later.

So pls do help me