Three things that help me sometimes:

1) Talking about it as it's happening. "I'm feeling far away. I feel cold. My thoughts are very slow" etc. This doesn't make it stop totally but does keep me present enough that I can remember what happened later. Also then I feel like she's still there and it feels less terrifying (and also less like a waste of time and money.)

2) Keep having sips of something. I think it's better if it's a hot or cold drink that I bring with me but if I don't have that, room temperature water (which she keeps available) is still good. It forces me to be somewhat aware of my body. Also my mouth is usually a desert when this is going on so the drink is a pleasant sensation.

3) stand up and move around. I discovered this by accident getting up to cross the room to get water the other day. It kind of broke the spell of sitting there in my own world.