Is it normal that fall in love with some one who is engaged

i met that girl in class and we became friends. she told me every thing about her life. she has a boyfriend. but slowly slowly she become more close to me and now each and evry moment i feel her. i can't take my foods and sleep properly. wherever i see her face apears. i can't concentrate on my life. I know we will never be together yet I can't prevent my feelings for her. she is from different religion, different culture. i dont know am i in love with her or not but i care for her. she is very cute and honest. i can't blame her. i just want to be her good friend for rest of my life. and control my feelings. i want to she her happy always. please help me out. thanks.......