Yes, you should give up on her.
She told you that she has a boyfriend.
There is nothing else to be said.
Even though, on the Thursday before last, she made you feel as though she liked you because she was looking at you, playing with her hair, smiling and touched you with her legs, she still has a boyfriend.
This means that she is not emotionally available to you.
Sometimes, a girl can show a guy a lot of signs of interest.
However, if she is in a relationship, those signs are merely temporary and of the moment.
There is still someone that she thinks about a lot more deeply and that would be her boyfriend.
It is best to not hold out any hope with this girl.
She is just not available to you.