Not that it matters but was she cheating?

Not that it would have any effect on the movie or storyline but I got the feeling that she was cheating on him.. A few times it seemed like they were going to take that route but never ended up pulling the trigger,She asked him if he heard the voicemail she left him and he said no and she told him not to and then that guy who showed up later in the movie tried to call her but she rejected the call and I'm assuming that was the same guy who called Brad at the beginning and asked how she was but Brad hung up.