Is my girlfriend cheating on me with my friend?

So we have all known each other for almost 3 years and she has never given him a nickname before because it is a little hard to come up with a nickname for him his name is Everet and just a few months ago she has started to call him evey and will ditch me as soon as she sees him and when we hangout together i feel like a third wheel and I'm able to just walk away and both of them won't notice for about 30 minutes. Ever since she started to call him evey she has been afraid of his parents and before this she wasn't afraid of them but now she is. Am i just overthinking this or is there something going on here? I don't know what to do i need some advice.

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Oh yeah and lately they have been walking so close to each other that there shoulders are practically touching each other. She also love to buy him candy and she just gives him lots of food all the time (no she only does this with him she will offer me food from time to time but that's like once every blue moon.) Oh and she always says that he is like a little brother to her.
Is my girlfriend cheating on me with my friend?
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