Definitely tell her. It can be more damaging to go faster than you are able to cope with.

I would also suggest being more honest with her i.e. if you are not okay, or if it isn't easy, please tell her so. There is no judgment in the room. And she probably gave you this assignment because you told her you were okay - when in actual fact, you aren't.

It's okay to proceed slowly, at your own pace. It is not a competition where one has to rush. Take care of you and check-in honestly with her. It would really help prevent you getting overwhelmed or struggling on your own...