Speaking from past experiences, after the end of a serious relationship I went through something like this as well. It was a way to forget and let out a lot of pent up anger or frustrations and get the attention I felt like I was lacking before. After a while though I realized I didn’t need that or want to be viewed that way anymore and so it stopped completely. And then I met my current bf who I never said dirty things to or send super explicit pictures to all the time because it just wasn’t who I wanted to be anymore. Over time with comfort I did because it was a totally different dynamic. When the phase ends it ends for a reason and I have no urge to ever go back to it. It wasn’t something I enjoyed half as much as I thought I would. I’d be willing to bet she went through something similar and within the few months before she met you discovered that wasn’t the person she wanted to be anymore. I’d let it go and definitely stop snooping through her phone.