Needs help dealing with guilt?

My friend and I are stationed in Iraq. When we were in training, she made friends with a guy in our unit. They became very close, almost like brother and sister, always picking on each other. She started to feel guilty about their relationship and all the time they spent together as she is happily married. I tried to reure her that she had done nothing wrong and especially in situations like ours (stress of deploying, 100+ males with only 8 females) it was natural to bond with people! He later professed his love for her and she stopped talking to him. Now we are here in Iraq and she is still racked with guilt! She wanted to tell her husband everything; I tried to discourage her as 1) she didn't do ANYTHING wrong and 2) all it would do is make her husband wonder why she held it from him to being with? She ended up telling him and he agrees that she did nothing wrong yet she still feels guilty! She realizes her guilty feelings are silly but she can't help but feel that way! HELP!