I think I'd try to help your daughter to see that although it may feel like it at times, her JW situation isn't an emergency and that there's no need for her take it all so seriously. JW's tend to think that the world is watching their every move and that everything they do is of global significance. Each JW is made to feel that they are personally representing the organization and even God himself. Even poor little Sophia in the JW cartoon video was made to feel that she had the ability to make the creator of the universe sad if she bought herself a little ice cream cone instead of giving the money to the Kingdom Hall.
Your daughter and most of us here, have been carrying this mental load our entire life and it's all so completely unnecessary. Nothing they've ever said has happened and there's no hard data to prove any of the things they believe in.
She is undoubtedly very anxious so I think I'd let her know that as far as you're concerned she's off the hook. She's free to choose to quit going altogether, attend once in awhile or to keep attending regularly so that she can see her friends and she can pay as much or as little attention to what's being discussed at the meetings as she chooses.
I'd line up a few names and phone numbers of Counselors for her to talk to and let her know that she free to decide whether or not to go see one of them if she thinks she needs to. In the meantime, I think you can help her understand that there's nothing wrong with her and that what she is experiencing is completely normal under the circumstances. Help her understand that she has complete control over her thoughts, feelings and emotions and can decide how seriously she wants to take all of this.