The fact that the girlfriend doesn’t want to tell her family is kind of a hint that they won’t be happy about the relationship. So being upset is kind of the best outcome in this situation.
It’s nice that you and also I have met nice muslims who encouraged their kids do love whoever they want. In this specific scenario I would trust the girlfriend though, because she knows her family better than us.
We’ve just been on the french north coast last week (from Austria) and I was also positively surprised. Everybody was really nice and spoke English very well. I’m still traumatized by 4 years of french in school because whenever I said something I was scolded that the pronunciation is wrong. Unfortunately that made me hate the french language, but french people made me more confident now and maybe I can set my peace with french now.