Should I be mad?

My fiance sent me screenshots of him and his friends conversation (it was a girl) he was just showing me what they were talking about. They never met, but i guess they used to be like bestfriends and they did like eachother at one point. Anyways, they werent flirting so i said okay. Later that night i seen the texts on his phone and in the screenshots he left out the message where she said "yeah lol i used to be like in love with you!!!" 
He hasnt flirted with her, and she knows he has a girlfriend whos pregnant. Should I be mad that he left that message out when telling me? I dont really want to confront him about it because hes been really stressed and im overly jealous anyways and i dont want to sound more crazy jealous or anything by asking. Especially when be has alot to worry about. I just am not sure how to feel about it. What do you ladies think. Let it go or be concerned?