This type of thread seems to crop up every few months
I don't really think that "pretending not to care" is going to work. It's pretty transparent, which is the reason that it occurs so often in Teen movies.
It may already be a lost cause, but imo, you should just ask her out. Say "Well, I actually still feel the same way about you. I'd like to get dinner sometime. How about Thursday?" It will be pretty obvious whether or not she is into you. If she is, she will accept. If she does anything but accept, including, but not limited to suggesting that you both do something with a group instead, suggests that that might be nice sometime but fails to come up with or refuses to commit to a firm date, tells you "as long as it's just as friends", spare yourself a lot of trouble, and forget about it. She isn't being shy, she already knows you, she doesn't need time to think about it, she just isn't into you. In that case, just move on. Don't make a big scene of it. Don't be a dick to her, but don't make plans with her either.
Oh, and taking a look at the picture below, she is not at all attracted to you. Notice her shoulders and the placement of her arms, and the distance between her front and your back. If she was at all attracted to you, she would be a lot more grabby, even if just being "friendly", and she would most definitely be leaning into you. Actually, this type of "friendly/funny" activity would give her an excuse to be grabby without her feeling guilty about it.