You could ask her to help you with this moment. Ask her if she will acknowledge it.
But she may not want to do that because it puts her in the position of giving you permission to cry, something she surely wants you to feel free to do, but on your own terms and not on her cue or as a direction from her.

It would be a really good topic/issue to discuss with her because it is important to you.

My T acknowledges my tearing up. It feels comforting when she does that and it's an opportunity to talk about where the strong emotion is coming from (now, before, etc).