My advice to you? Step off. Horror Mickey mouse shirt, perhaps that would be the time to try again. Until then, respect the boyfriend as you’d like other men to respect you. You just can’t fall in love without having conversations with that particular girl. Love, at first sight, is shit, so just don’t roll in that. What I’m trying to say is you must know her well. Because if you don’t, then it can’t be love, you must be jealous of her boyfriend. If she loves him deeply and with maturity, then it’s time for you to give her a side. Just be friends and don’t be that guy who follows girl everywhere and starts smoking and drinking etc.
Now if she’s confused whether she loves Horror Mickey mouse shirt, then you know it’s your turn to give your 100%. Do what she likes, take her out, respect her (and her family also), be honest with her, try to spend as much time as you can with her. But don’t be creepy as well. Do all the things that you once wished to do for her and most importantly. If you feel frustrated and suffocated because of the situation, just go and tell her everything. Everything that you feel about her. Because you never know the entire scene weather she is really committed or not.