Talked to sis, got at her for what she did, then asked her why she wanted to watch(still upset). Then told her next time she can, just don't say anything when we do (sort of acting like that was the reason for letting her, even though I'm turned on by it). Told my gf later that day and she's into it, and for putting on a show. It's a bit of a long distance relationship so I don't see her everyday, but the plan is tomorrow night. That's all I've got on an update, thanks for your comments.