Ways to make sure she likes me back?

Alright so I'm a senior but i had to take a elective class i missed. Freshman take the class too and i have sat next to this freshman girl sense the beginning of the year and she is the cutest girl I've ever met but I'm not 100% sure she likes me. She always smiles at me whenever I look at her and being the shy guy i am I end up looking away and then if she isn't smiling she smiles then. Also last Wednesday I was talking to the teacher and i didn't know she was in the class so I turn around and we lock eyes and she gives me the cutest smile I ever seen in my LIFE. she also "booped" my elbow, and "beeped" my class ring, i know immature but i find it cute she also asks questions about me all the time and she asked me Thursday if I was mixed (which i am) and she said "so.... does that make you a milkshake?" weird i know but cute, and then i said "yea..." and she said "Its ok im a milkshake too, in fact everyones a milkshake in a way" like she was trying to comfort me.. Although the signs are all there i still want a sure way to find out. Any suggestions?