Mom Went Through My Icloud Messages

My mom 58F and I 32F have a VERY rocky realtionship. She's been letting my kids use my IPad while iv been working on the slope and has been looking through the messages sent between me and my fiance 33M. She went through all of our messages and found some stuff she didn't like. She is now threatening to publicize said messages and take me to court. Is the messages she found legal to be used in court? What should I do.

Edited to add: she read some messages from a relapse I had last summer (June 2024) I know this was wrong and I'm wrong for that but iv already been talking about it with my therapist since and got back on my regular medications. She took her own screen shots of this conversation and is wanting to post them online to make me look bad and take custody of my children.