My guy friend wants to take me to dinner?

Except he has a girlfriend. No drama with it, just that we work together an we get along very well and hug a lot and flirt. I initially had a crush on him, but kept my feelings at bay sincere found out he's taken, and in love. He insists on hanging out with him and his girlfriend and his girlfriend told me he likes me a lot, and the best at work. I covered one of his shifts this week and he said he'd like to take me out to dinner, but he'd bring his girlfriend along "so it won't be awkward". Am I just thinking it's fishy because I have a small crush or is something up?
My guy friend wants to take me to dinner?
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