I don't trust her

Okay so my yonger sis is very friendly with her vagina and some how whether it's on purpose or unintentionally she always end up fuckin with or on someone one else's man. For example the child she has now is by a married man. She has been doing this since high school. I knew not to bring my boyfriends or lil boo thangs around but now Im getting married. Im worried that she's going to be trying to flirt or worse. Just seeing what she has done to members of our family gives me valid reason to be paranoid.......... IDK advice please