is this weird?

My mom is constantly on Facebook. Sometimes, she Facebook stalks my SO's family. She knows I don't like when she does that, so she tries to hide it, but I usually find out. I feel like she's a teenager and I'm her mom with the way she tries to hide things from me. Today I found out that she was creeping on my SO's little brother who is a freshman in high school.... I just think it's pretty weird. Maybe I'm overreacting, but it makes me feel uncomfortable. My SO and I are both 22.