>>81610546
She was flirting with you.
For psychological reasons, girls dislike making the first move, so when they do make the first move (like asking for your number) they always come up with some false pretense for why they want it. In this case, she said it was for "advise and coursework help" but the truth is she was into you and wanted to get to know you more. Girls just never say it directly because it is expected that the man makes the first move, so it's shameful for a girl to be so direct. Makes sense?
By refusing to give her your number after she made several desperate attempts (asking directly, then insisting you promised earlier, etc), she assumed you had no interest and rejected her. She has no idea you were clueless to her intentions.
If you want some general advice, don't have such an autistic stick up your ass about things like this. Just because you only wanted to talk in the moment doesn't mean you can't go with the flow and accept the spontaneous opportunities life throws at you. Next time, take her number if she's cute, and when you start texting her suggest you meet up for coffee to talk more. That's called a date. Do that a few times and you have a girlfriend.
If you you didn't find her cute, then no harm done.