I would tell her "hi, I've seen you around here a lot but we have never spoken, I'm xyz".

It seems to me that she is really into you so she should be open to talk to you.

After that talk about stuff that makes YOU laugh, that makes YOU feel good - if you feel good then she will feel good and add flirting and see how she react to it.

If she ain't feeling the flirting then tone back.

I would advise reading this guide I was suggested in the comments a while ago on how to flirt, keep interactions going, how to set up dates, how to text etc that has helped me a lot over the past months.

Hope it will go great.