HELP! I'm 17(M) and I like a girl in my class she's 17F

We know each other for 4 years she's a good friend of mine but suddenly I have started felling a spark whenever I see her (we go to the same tuition but barely meet throughout the week) and basically I'm somewhat stuck as she always chooses to sit beside me in tuition, one day she randomly started walking by my side and started asking me why I was going home alone(as my friends were absent that day), one day she randomly started fixing my hair saying something is stuck there,she in general don't talk with anyone about her childhood but she even shared me where she went on a trip when she was 12y/o, she yaps about her previous school, she laughs at my weirdest jokes etc.

But she's completely different online, we generally talk about academics in DMs and nothing else and it's always me initiating the conversation, and majority of all our conversations are dry and cold.

Shall I confess her atp or she's just playing with my heart as sometimes(I would say yeah it's noticibly high number of time) she just leave on read or doesn't respond to my text at all.

Pls recommend me on what to do.