What does it mean when a girl ties her hair up?

This girl and I were working on an assignment together and I am pretty sure she likes me. Anyways, she randomally tied her hair up and then put a bit of makeup on her lips. Is that a sign she could like me?

Prior to that we both spoke in the Uni cafe and got to know each other and she is always smiley as am I
What does it mean when a girl ties her hair up?
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