I m in 12th standard and I like a girl from class 10th but she is committed already

I m in 12th standard and I like a girl from class10th .she is in my class only. And our goals are also similar. I don't talk to her. 3 months before I gave her a sketch of herself which is dicto. That day she messeged me that brother I m already committed,sketch is good so I had taken it and I m least interested so don't assume anything. Whole class knows rather whole boys know that I like her . She also knows but I don't have any intention to propose her but my frnds tell that the sketch is equal to proposal . I can't live without her I have strong feelings for and I know 90 % chances are no relationship will form I don't know what she feels about it why she never talk to me if she is frustrated as the whole class knows it and maybe tease her with this she sometimes just smile nothing more she even not reply to me on fb as I just wished her happy Diwali (a festival in india) what should I do should I tell her my feelings for her or not express my feelings plz answer in detail