I was an anxious teen. It's hard, as you know.
1. Read "the childhood roots of adult happiness." It lays out excellent advice how to build lifelong confidence, how to learn to make joy and overcome adversity. The most important key is that your kid feels a sense of connection, belonging in the world and has confidence that she is an able, interesting and liked. Of course it takes time to build it, but I would bet that would ease her anxiety better than drugs alone.
Please read that book. I sincerely wish my parents had.