I think Adriana seems naive, and Marko doesn't look honest to me. There's something about him that seems shady as hell. She might've forgave him more than once for cheating for the sake of her kids..but I highly doubt Adriana would cheat on him. She just doesn't seem like that kind of person. If anything he might have since she was always away from home, and he seems to have that jealous personality. None of us here know Adriana personally, but to me it just doesn't seem like she can do this.