Why can’t I make her happy like he does

I’m in love… I‘be been in love with this girl, my best friend, for nearly 4 years. Sad right? I’m actually her temporary roommate until my electricity gets turned back on, I’m 16 btw. Which is all fine and dandy except; her boyfriend lives across the street. There 1st year anniversary is coming up, it’s tomorrow actually. I’m currently sitting on her living room couch trying not to cry. Why couldn’t she just fall for me? I know it’s selfish, but damnit! She was my first kiss and my first consensual romantic anything!! But he’s strong and tall, he’s kind and understanding, well most of the time. I’m like that too I think, at least I hope I am. I refuse to say anything about my pain to her. I encourage their relationship because she’s never been in a healthy one before and he’s not abusive! I just want her to be happy, I want her to be comfortable and feel safe. I want her to be her self. I love her, all of her; her acne scars, her hair when it’s greasy, her messy eating. I love her, I love the way she does her make up, loves how she wears whatever she wants no matter what anyone else thinks, I love how kind she is, how she always does her best. She’s not perfect, and I don’t want her to be. I’m trying so hard to be a supportive friend but it’s killing me on the inside, I just want her to love me the way I do, but I know, that won’t make her happy.