Should i tell her how i feel about her?(even though she has a boyfriend whom she adores)

There's this really cute girl that i really like where i work. She has a boyfriend though, I don't want to come in between them, but i really can't stop thinking dreaming about her. I've never had this stupid feeling about anyone, where i'm worried about her when i don't see her; like when she isn't around im wondering where she's at and what she's doing. I just wanna stop liking her so much. She makes my day every time i see her beautiful smile, i haven't told her how i feel about her, should i tell her? She's got the most beautiful smile and the prettiest eyes ever. I think i deserve her, i would treat her like a princess, and would cherish her forever if she lets me. BUT she looks happy with her boyfriend.