Am I overreacting?

I(25 M) am in a 4 year relationship(long-distance) with 25F. Recently she went out with a male friend(25) whom she met online through her friends. They went for a movie late night in his bike and spent some time. Initially I thougth it was okay, but now I feel very disrespectful to our relationship about it. Is it normal for people in a relationship to go out with other gendered friends. I know for sure that nothing bad happened there, yet the thought of it makes me feel very disrespectful. What should I do about this.