I don't know about the holding hands stuff. I would wait, you don't want to pressure.
Everytime you do something that feels romantic that feels uncomfortable to her simply reminds her she is not feeling the same way 'YET'. But they don't add the YET to the sentence.
I would ease in, with maybe a touch on the back or shoulders if the opportunity strikes. Maybe helping her into a ride, or when holding a door for her. It's less assuming and less threatening, yet still requires a level of comfort that only you and her have.
Think of light hearted ways to flirt. Think first/second date. Win her a stuffed animal, share a Icecream cone, etc.
