I'm trying to learn what to do in these situations so I have an idea of how to improve in the future.

Situation 1: I asked a girl out at the library that I've been seeing around and she was really flattered but said she couldn't because of how busy she is in school and she's not looking to date. She insisted that she didn't want me to feel like she wanted nothing to do with you but she just didn't have time as she's always studying. I buy it based on hard she studies but I can also understand if she just isn't interested...I got her email as she's in the same uni program as one of my friends who graduated and I said I could get my friend to give advice. I didn't number close to feel pushy but since she's turned me down, is it alright for me to hit on one of her friends?

Situation 2: I got the number of a stunning and friendly 18-year old in art school....we talked for 30 min and before she left, I got her number. We were talking about a day to meet up and she told me that she had a bf but said we could hang as friends. How would you approach this situation? Would you still try to meet up? Thanks!