How do I know if my mom read my diary?
It works with intelligence agencies why not a personal diary.
Put worthless information in good format of your style and when or if mommy reads it and either A confronts you the moral high ground is yours.
B is when using probing words you can positively incriminate her for such a breach of trust and apply guilt in heavy measures.
Word to the wise don't go insane or outlandish with what you write as false information.
Use simple but easy things.
Example, Bought a toy today it's really fun to use asked my friends to keep it on the down low incase the parent ask.
This isn't only ambiguous it has alot of implications to parents it's also gender neutral since I don't know the Op'S gender.
If your parent blows up at you for such implications you have them in the moral low ground and can really drive the peg of guilt home.
Especially when said toy is a game or non sexual item.
Try to make subtle questions randomly of things she should not know.
Like what did I do at school yesterday or so…
Make it look random, don't stress it, if she asks why or what don't say anything.
Do this for a while and try to connect the dots.