When my eyes start to get watery, my therapist will often ask me what the tears are for, sometimes I can tell her, other times I can't.

Sometimes if she notices a change in my voice, she will say something like, I can tell that this subject goes very deep for you, or is more painful than what you show.

If you feel it may help you that she addresses it when she notices it, I would tell her. She may be avoiding it because you have mentioned the uncomfortable side of it to her.