Writer's Fallout Shelter

I have never had to deal with the situation you are describing in real life or in fiction, but I do tend to kill lots of people in my WIP. How the characters deal with death depends a lot on their individual personalities and past experiences, just as a real live person's response would depend on their personality and past experiences.

I would say that the reason you are feeling conflicted about how to portray your character is because she feels conflicted. She loved the guy. They were engaged to be married and were planning on spending their lives together. Those feelings weren't just turned off when she met lover #2. And before she could resolve them, the decision was taken away from her.

So, how besides crying could she show her grief? Well, she could become depressed -- as you said at one point she loses her will to live -- and stop bathing, cleaning the house, leaving the house, or doing other things to take care of herself. She could walk around smiling and laughing inappropriately, denying her feelings. She could refuse to acknowledge the death and keep planning their wedding. She could get rid of all of his personal affects or refuse to do so. She could get angry.

One thing you might want to do is google the grief cycle. Some of the things written about the different stages of grief from a psychological standpoint might be able to help you out.