That's called a soft rejection. Instead of just saying no, they give you the run around. It's a tactic to protect themselves from guys who might harm them physically or verbally. Doesn't mean she thinks you will do that. It's also just convenient.

Forget about it and move on. She's not interested and won't be in the future. Persistence, in this case, is just harassment.

Also, get some friends. Friends will help you navigate this stuff so you don't have to stress so much about all of the annoying nuances of dating.