Such crashes makes me extremely aggressive, expecially with objects. I have noticed that people who become very aggressive as a result of biochemical disequilibrium, are otherwise very sensitive people who would never hurt an ant. It's the case for me. I have never hurted anyone or hit whatever person, I hate violence and can't even stand violent movies. Yet I get uncredibly aggressive and angry when my blood sugar swing happily. Irritability is the worse: when even the voice of someone you love gets on your nerve for no reason at all.
I have been suffering from hypoglycemia since I was 7 and I remember at age 8 getting angry almost daily to the point of tears just from watching "stupid" commercials that made me angry. I also got angry to people in motorcycle and to comic movies without any reason. A lot of things made me mad and only after my diagnosis of hypoglycemia I began understanding why and all the strange feelings I had as a child.
The good thing is that the more aggressive you're on a sugar disiquilibrium, the more balanced you discover to be once your blood sugar is on an equilibrium, it's a wonderful sensation and you will attract more friends and great opportunities than ever. You'll also realize that you probably are more capable of loving life, people and being in awe with this beautiful world than other people can.
There's a book about a woman who was diagnosed as mentally ill and put on a cocktail of dangerous psycho drugs. Her life was miserable and she was suicidal. It was reactive hypoglycemia from the beginning. Your girlfriend should read that book.