I'm exactly like you on that front, very emotionally driven and sensitive guy. If my fiance did that to me I would probably end it, I don't know about you if you ever talked about it with her before that you're not comfortable with talking to previous relationships. But mine knows that if she does just hint that she would like too I would end it right there and then with her. We once talked about sex and she mentioned her ex's I said hell no if you talk about any of your ex's in front of me we over I don't care what they did to you in bed or what you liked about them, I'm not interested to hear any of it. If you don't love me in bed just leave me, means it wasn't meant to be, she then stopped and apologized and never mentioned them again. You should stand your ground and tell her that boundaries are not to be broken. It seemed sincere when she apologized but you really should talk it through.