Interesting story. I don't think I'd have done anything differently than you. At least, nothing that you put into print. There are a couple of things you didn't say, though. The first thing that comes to mind is this: what method did you use? Reason why I ask is this - the previous poster said: accidents happen, your hand can slip while lowering.

Well if the belayer uses two hands to lower the climber (which is what I always teach) - then no - accidents don't just happen. If for whatever reason (a kink in the rope) one hand gets knocked off the rope, you have another hand involved.

So - what did you teach?

As for whether to allow her to belay you or not, I'd say there are two things I'd be concerned with if I were you:

1 - Are you overly anxious about the belay? If this is impacting your climbing, then you need to look after yourself first. Maybe after you get your head together, you can go back to helping her.

2 - Unless and until you are both clear on what went wrong and why, I can't see how there's any guarantee that what went wrong before won't go wrong again. You don't just drop a climber when you're lowering them. Several things have to have gone wrong for that to have happened.

I've seen belayers dodge 10 ton blocks and catch a climber. I've personally gotten yanked upside down and dragged ten feet down a slab and never let any rope slide through the belay device. I'm not saying that a belayer using an ATC competently could never drop a climber, but I'm just saying that it should be a truly exceptional event, caused by many factors going wrong at once. To have it "just happen" is simply not acceptable. Rather, a combination of poor technique, poor application of that technique, and/or poor attention must have been involved.

GO