13 year old DD has a friend who "helps herself" to things in DD'S room without asking. These things are not big things, but DD gets upset that she isn't asked. For example the friend helped herself to DD's cotton wool make up pads and used them all in a craft project she was doing at our house. She took some of DD's craft paper home apparently even though DD asked her not to.
I have Aspergers and struggle to know how best to deal with this. Should I "Have a word" with DD's friend myself to ask her to stop helping herself to stuff without asking or is this too heavy -handed? I don't want to over-react as each incident isn't anything huge. However, I want to somehow help my DD stick up for herself and establish boundaries.
Thanks for any advice.