I suggest some simple small talk and smiling. Small talk is about safe non personal things that you might have in common. In a lecture, ask to borrow a pen (pretend yours is out of ink or lost) double check the assigned homework or reading pages. Ask if she knows where the closest vending machine is (as long as it isn't within sight). Remember to smile and say thanks no matter what the answer is.

I used to struggle with self confidence and social anxiety. I started using small talk with cashiers to practice. If I paid cash, I'd ask for all the bills to be singles. I'd say it made making change at the laundromat easier. I would ask someone for directions or if they knew a place for good chicken wings or a good cheesesteak. It didn't matter if I needed directions or change or whatever. It helped me practice talking to people, listening to people and thanking them. And smiling because I was always so anxious it felt like I couldn't smile. I practiced smiling with every thank you even if I couldn't manage small talk.
It helped most with social anxiety. Confidence took a bit more time.

Good luck.