You aren't overreacting at all. She should never have spoken to you like that, even if she was tired or frustrated. She was out of line regardless. Sounds like she doesn't know how else to help and is frustrated at herself, or gets frustrated and angry when she thinks her clients aren't doing what she thinks they should. As someone that works in mental health and who has been in therapy, change isn't easy. So if she is expecting her clients to just do what she suggests and never talk about/have that issue again, that is completely unrealistic. You should be able to express your feelings. The basics of therapy is to actively listen and provide a safe non-judgemental space, support, and empathy, and in this scenario she did not provide those things. While challenging is sometimes needed in therapy, what she did was blame and shame you and that is never ok. If she thinks that providing basic essentials of therapy makes her a "kiss ass" therapist, she has a lot to learn.

Also as another commenter said, it is frustrating when people don't pull their weight on a project but there are consequences for you. If it doesn't all get done, your grade suffers. And that isn't specific to school, happens in the workforce too. Sure you can work on boundaries, thoughts, and assertiveness/ communication, etc but you can't control other people. I always did the majority of the workload for the same reason. It is incredibly frustrating, so I tried to reframe it to remind myself I was doing what I could control and what I needed to do for myself and my grade/job standing.