"-have her practice slave positions while thinking about you...(God, I love that, lol)"

While I love this too, a more "public" thing you could do is some sort of "posture training". Have her cross her legs all ladylike, arch that back a bit, sit up straight, and make her hold that for a few minutes. While she thinks of you.

Strike a pose, as it were.

Much like assigned clothing, it's really rather subtle, and functional in a variety of locations, which is part of what I like about it.

I must say I also like the idea of having her write out what she was thinking about when she touches herself a lot. Assuming you let her touch herself . Talk about fun reading in the evening.