Katy
DBH and I always keep our cards to each other upstairs, ever since MiL looked at my valentine's day card to him and found some handmade 'vouchers'. Maybe it depends on your family, but we were taught that they were private, like letters. She obviously doesn't think like that. She is very nosy, so now I am nosy back - and yes, I do look in her garage and rooms when we go to stay, because she is such a hoarder and I am the only one who keeps on at her to get rid of stuff she doesn't want or need. She doesn't resent it, she needs it, she just doesn't want help doing it, only needs motivation to do it slowly by herself, so I ask if she has found anything interesting or exciting lately, any family jewels etc. I know she is nosy because I once hid something from her - and she found it! Now I have no qualms where she is concerned.
She found a whole box of her father's paperwork that she had never opened since a few weeks after his death almost 40 years ago, last year. I can't live like that. Sadly, DBH is also a hoarder, I have watched his study become more and more cramped until he cam barely get to his desk. I refuse to let him spread further, he has a loft access in there so he must spread upwards. MiL will be most upset when he does, she loves rootling around in there!