:^)

Nobody has the right to tell you something like that and to then expect you not to act accordingly (especially when the safety of your children would be at risk); your sister chose to get herself involved in the issue between you and your mom.

"...do I ask her directly and get my sister involved?" - Why would you not? Are you more concerned about your mom and/or sister becoming annoyed with you (though, your sister expecting you to keep it to yourself after telling you such a thing is ridiculous), or for the safety of your children?

So apparently making others the unwilling targets of your exhibitionist desires is perfectly ok (even "triumphant"), provided you are a woman?