Yeah. Feeling "relief" makes me think she was feeling guilty for having cheated on him and went looking for evidence of infidelity in his part to relieve her guilt. It would also explain why she didn't feel angry about it. Afterall it's "a wash." They were both guilty. If he was the only party at fault you can rest assured she'd feel betrayed. I'm also basing this on experience. When someone starts accusing you out of the blue of cheating and goes out of their way to cross your boundaries, invade your privacy and look for evidence you're cheating you can bet it's because they're having an affair and looking for a way out where they don't come off as the bad guy. Also this is r/relationships where every post seems to go out of its way to present OP as a perfect angel and their partner as an evil villain.