Can a guy have female friends while in a relationship? by NYC Robert

This question dawned on me when I had asked a girl (I don't know her very well, but it seemed like we share common interest), "Would she like to get some lunch?" At the time, she knew enough about me to say that it wouldn’t be appropriate, solely because I am in a relationship. Though I had a feeling that would be her answer, I didn’t quite understand. She went on and on and simply concluded that it wouldn’t be right. Still, I didn’t understand. I then turned the scenario around, and asked her if she has male friends. Turns out, she does. I dug a bit deeper, "What's the difference between them and me?"After we discussed it for a while longer I realized she wasn’t saying much, just repeating herself. She also wasn’t stating much other then, "Because you're in a relationship."