Would it be okay if I told my girlfriend that she wasn't traumitized?
Why do you feel the need to tell her this?
Her professor said she was traumatized in 2013
It's not up to you to decide if an experience was traumatic for someone. It's a big moment in their life and they can feel about it however they want.
If she is going to be like that I'll dump her stupid ass.
That might be better for her, because people who have dealt with trauma need people in their lives who care about them and are able to empathize with them. You should never tell someone who went through things like that that they aren't traumatized.