How can I help my girlfriend realize her family is emotionally abusive to her?

Helping girlfriend. That is not easy , and what u call abuse can depends on age , culture and how close she is to her family. However, if she feels being abused than there are many ways to deal with it.
She Knows. She knows they are emotionally abusive. The real question is why does she put up with it. Typically it is because she is not ready to step out on her own just yet. Teh best you can do is don't be critical of her family; simply be supportive of her and show her what a supportive and emotional nurturing person is really like. Having a supportive person will give her the strength she needs.