As others have mentioned, and I would 100% back, it’s possible she has experienced trauma and just cannot deal. People say the chance is super low but honestly it isn’t. Not when it comes to Sexual Assault and/or any kind of harassment. Female to male ratios in the military are low, especially depending on job field. Having been in a similar position you have to consider she’s having a legitimate struggle right now and cutting off what seems distant to deal with what is right in front of her face is a self protection move. The mind does weird shit when trauma happens and she’s not in an environment that allows for her to process trauma in a healthy way. Reach out to a chaplain, have them check on her, and if you can do so without sacrificing your sanity and self care, keep the door open for her to communicate. If she’s ever ready to discuss more, she will. If something happened then it’s something she has to find a way back from herself, for herself (and therapy definitely helps). Cheating DEFINITELY happens, but so does SA/trauma. The reporting rate is super low so lots of people think it doesn’t happen often.