Different therapists have different ethical rules about what gifts they are and are not allowed to accept, and also different therapists may have different personal guidelines about what gifts they are comfortable accepting.

Where I am, and in many other places, the ethical rule is that therapists cannot accept gifts of "greater than token value." A small handmade plush would probably count as "token value" unless it's made out of really expensive material or something. So it may be something she could accept. But even if she is technically allowed to accept the gift, that doesn't necessarily mean that she will accept it-- she might still feel that it would be inappropriate or harmful. So there are no guarantees!

The good news is that it's her responsibility to determine whether she should accept the gift or not. There's no rule saying that you aren't allowed to offer. Just be prepared that she might say no, not because she doesn't like you or because she doesn't like the gift, but because the way she understands her responsibility as a therapist doesn't allow it.