Is it still worth it to like to someone even if they like someone else?

Sorry if that question was confusing. I’m a sophomore girl that just transfered last semester to my school, so I have no friends. The only friend I made was in my orientation group. She invited me to hangout with her and her friends, here is where I meet “A”. I was immediately attracted to her, so I obviously continued hanging out with her and our other friends. Me and A decided that since we’re so close we should just live in the same dorm. Which is when after a few days A told me that she had a “crush” on me. After she told me I told her that I also liked her. Every other night A will text me non stop, or just not respond at all. A met this boy named J which she started talking to him and giving him all the attention. I was completely forgot about. After hooking up with A, even that happening still makes me nothing. The only time I talk to her is when I have to. Which would be during class. She told me she had a crush on me, but now she’s always with J, and sleeping in his room. I mean obviously she likes him. But I was lead on and I really like her now. I don’t know if I should dorm with her because I would get too jealous. J is a senior, and it’s clear this senior guy is purely using her. I met A only 2 weeks ago, so I really can’t say anything to her rudely. If I got in a fight with her I would lose all my friends. Thank you so much in advance for reading and responding to this. :-)