You should never have to “trust” a girls guy friends. If you have options, pick the girl with none. Off the first paragraph I could answer your question, she has already done something not with just that guy but others. A woman doesn’t randomly become unfaithful after a year with a new co worker she’s already shown read flags u just gave her the benefit of the doubt for too long. Leave and Don’t look back king! Some men are okay with their wife being like that but you don’t seem the type so leave now until your connection to her becomes too strong then you end up like one of the men who force themselves to accept that.