I really like this girl, but she’s already dating another guy. Well they’re not just dating – they actually live together.
Should I tell her how I feel?
I admire that you got straight to the point with your question, so I’ll get straight to the point with my answer: No, you shouldn’t tell her how you feel.
Nobody has any business getting involved in, or interfering with, another person’s relationship, and that includes even if you really, really like them. The only thing you’ll do is cause arguments between this couple, and both of them will resent you for that.
Let’s throw out the idea that you do actually tell her how you feel about her, and she suddenly decides to leave this other guy and be with you instead. Could you really trust a woman who’d just get up and leave a relationship because some other guy told her they really liked her? Wouldn’t you hate anyone interfering with your relationship like that? I would. Why? Because it’s totally and utterly unfair to do that to anyone.
There are millions of single women out there dude – go find a single girl you really like and share your feelings with her instead.