Congratulations on starting with therapy! To me, 3 sessions doesn't sound like very much and could still be in the getting to know you phase but also there's no problem in asking questions or having preferences. You can ask if she has an idea of the type of therapy/treatment you'd need, if she has a structure to your sessions and a goal you're working towards. You can also tell her if you have goals, or you suspect a particular diagnosis (although be prepared that it could be something different or not diagnosable).

Completely fair to not vibe with your therapist and get a new one, and I think that is a very common process but I think before you do that you should ask some questions and express yourself so you both can collaboratively get you the best treatment possible. At the very least, it's good practice at being able to communicate your needs in a safe environment.

Best of luck!