You're definitely not alone.
I used to feel the same way.
Most times I would feel like I wasn't actually getting anywhere because I never knew how to say what I needed to.
It's a very frustrating feeling.

If you've had a rough week, maybe you should tell her. That's what she's there for, is to listen and try to help you work through things.
Also, it's neat that she invited you to email her. You ought to give it a try
Sometimes when it's hard to speak up, typing things can be a little easier.

If you think you might have come off as rude or standoffish:
1) She'll understand. I'm sure she sees that all the time.
2) Maybe emailing her and explaining your frustrations or just explaining why you were being quiet, might lift some weight off your shoulders.

Emailing really could be a great thing and possibly help the face-to-face conversations glide along easier.

I would suggest that you don't give up on her yet, though.
It just takes a little time to warm up.
You said you love going and feel like it helps sometimes. So you gotta weigh it out.

Best of luck! Keep us updated!