Advice?

Okay so this is my senior prom and I really want to go with my boyfriend. Before me and my boyfriend got together I told my best friend that we would go to prom together but this was before I even became a senior. My best friends a junior so she also has her next prom that I could go to with her. When me and my boyfriend go together she always knew that there would be the chance of him asking me and me saying yes. My boyfriend and I have been together for seven months now and he really wants to go with me. He missed out on his senior prom because his dad had passed away and he was really depressed and missed out on most of his senior stuff. Well now she completely mad at me for wanting to go to my senior prom with my boyfriend. Am I wrong for this? I’ve asked her multiple time if it’s okay if I go with him or even bring up the idea and she just blows it off. I need advice on what to do.