I Need Advice On Getting Into A Relationship With A Girl Whos Already Dating Someone Else?

Yeah, just because she is going out with somone else doesnt mean that she doesnt like you! she might like you, just not being able to tell you! dont try to ask her out when she is still going out with him, but if they ever break up, then ask her to hang out, and she might say Yes! so it is Truely possible that she likes you.