You will find out with time, if this was a good choice of a drug or not, or it may be a temporary medication.
What is important - that your dd stepped out, and little by little, she may get more comfortable with these new behaviors, and eventually through counselling, and more and more use over time, she may be able to use these new behaviors even without medication. That is the goal, as there is no medication for BPD. But medications DO help if they stabilize the mood, or reduce anxiety, etc.

In the meantime - it's good news.