AITA for not asking my girlfriend a question?

My old professor and I still talk or email. I ask her questions and she sends me articles on biology. She has a PhD in biology so if I have a question about biology and I send her a email and she responds back. Now last week there was a article about the American health system. I couldn’t understand a thing it was saying. So I sent her a email and she explained it to me. My girlfriend found out and she asked why I didn’t ask her. I said she is good at explaining these kind of things. She got offended saying “you don’t think I’m smart enough to explain these things” I said you are smart but she studied this subject for a long time. This is her career. She also gives me insights I wouldn’t have thought of. I said “she can take these complicated subjects and make them easy to understand which is hard to do. via /r/AmItheAsshole https://ift.tt/2G37rpr