Voluntarily put yourself in the friendzone if you /reaallyy/ like her.
Don't be too overly friendly, don't be touchy-feely.
Just be kind to her, be there when she needs you.
Casual chats, y'know? Just to hang out.
Works if she likes watching movies.
You can be her movie buddy or something.

Like.
I love watching movies in theatres, but sometimes I don't have anyone to go with.
And going alone is one of the saddest/lonely/GIRLYOUCRAICRAI things ever.
Unless you're a strong independant woman who gives no poops, or a manly man who's watching action movies because manly.
Or something like that.

If you become good casual friends, enough to go hang out and get a meal together sometime, don't insist on paying.
Because things. Always have enough to pay for both if she can't, but it'll probably make her feel safer if you both just halfsies.

S'kay bro.