I've never had anyone try to sabotage me, but I have had the problem of too many cooks in the kitchen. I'll never forget my first Thanksgiving cooking for both sides of the family, with both my mom and MIL in the kitchen, disagreeing with me and each other about how to cook a turkey. The one thing they both agreed on was insisting the turkey needed to come out of the oven too early (I disagreed, but was overruled). It was raw in the middle. All of a sudden it became my turkey again. Yes, to this day, the official story is that I was the one who undercooked it.
Anyway, I learned two things from that: 1) An instant read thermometer is my friend. 2) No one else should be in my kitchen yammering at me when I'm trying to cook. Every time I've had people in the kitchen "helping" or just wanting to be in the middle of things, it has caused confusion and delay (bonus points to anyone who recognizes that fine literary/dramatic reference
The first item was easy. The second is something I still struggle with to this day. Sometimes I use humor to keep people out of the kitchen, pointing out that our kitchen is small and I am clumsy and "Spill hot grease on someone and suddenly you're the bad guy!" or "Sorry, I just don't work or play well with others." Sometimes I try to be polite but firm, saying "No thanks, everything's under control," which makes my mother sulk sometimes, but that's still preferable to the chaos of extra people in the kitchen (because somehow, one extra person always becomes several extra people milling about). I also use stealth. Seriously. When all else fails, I try to sneak into the kitchen when it's time to get the turkey out, in hopes that I can do all those last minute things with as little interference as possible. Sometimes I've even had my husband cover for me, and keep my mother engaged while I sneak to the kitchen!