My guess is that she is laughing at herself, like Artie said. Sometimes we just recognize our own reflection in whatever is being talked about and laugh at our own thinking.

I think we sometimes tend to assume others are laughing at us when in actuality, it is mostly about themselves. Kind of that inner dialogue, chuckle, at ourselves.

I used to assume judgment from others a great deal when I was less secure in myself. I've found as I've gained internal confidence, I am quite willing to laugh at my own thinking, and sometimes those laughs come out externally.