My first thoughts are that she might be mildly epileptic. She doesn't even realise she is doing this. What she may be experiencing are mild momentary petit-mal seizures. The seizures may be so brief no one notices but enough for her to temporarily lose her faculties - hence the accidents.

I had a chum at school who went through this - and the resulting bullying - right up until she was finally diagnosed with epilepsy at the age of 15.

Good luck.