you got some really good advice on communication about the underlying problem and encouraging her to talk to her therapist.

For practical steps to make the trip easier on her, talking in the evening is a good approach. Depending on her personality and coping mechanisms, you could also ask her to do something for you on her trip, like send you pictures of things that are special to the place she is going to - seashells if she goes to the beach, bagel shops if she goes to New York ... something like that. A task to simultaneously distract her from her anxiety and connect her to you.

You can also plan something special for the day she comes back from her trip to celebrate her overcoming her anxiety and to give her something to look forward to.

Just some little things to distract her from these overwhelming feelings.