Same here, while this was a few years back it's still relevant. My girlfriends parents are helicopter parents and would have a back door into everything if they could. So the one day I noticed that her mother had said to me that she doesn't mind us going to movies two weeks from then. This was only said between the two of us in a text. This was a good opportunity to switch her over to signal. She asked me if there is a way to check if she was in anything else so I had her change password and move over to a password manager instead of the paper notebook in her room that her mother probably looked through.

Only a week later her mother did look through that notebook at one point for passwords because because she openly asked for it one day "so she could check her school email for scholarship information", didn't ask for just the password, but the whole notebook. From what I remember my girlfriend had a conversation with her mother about privacy that would turn into an argument.

Moral of the story, even people you are told you are supposed to trust aren't trustworthy.