My husband's phone encryption

Yeah girls, we’ve been married for three years and my wife’s phone used to always be out in the open, but for the last month, she’s been taking her phone with her even into the bathroom. Plus, she changed her password. When I asked her about it, she says she’s just fiddling with it because of her coworkers, but honestly, it doesn’t sound convincing. I have a bad feeling inside; do you think she’s really hiding something or am I overreacting? I don’t want to start trouble out of nowhere, but I can’t sleep at night anymore.