AITJ for telling my niece she can invite a girl friend while petsitting but her boyfriend is not allowed?

My wife and I will be gone for 2 weeks and I’m paying my niece to pet sit and stay at our home.

It’s a pretty good gig for her because she gets to live there, eat anything she wants in the house and just take care of the pets while also receiving payment.

She asked if anyone else can come over.

I told her a friend that’s a girl can come over sure.

She asked if her boyfriend can, I said absolutely not.

We also have cameras by the entrances and I told her if she breaks the rule, she will not be paid.

She thinks it’s unfair and doesn’t understand the problem.

Well, the simple truth is I’m not having some guy living in my place 2 weeks having sex with my niece in my house while im away. Maybe it sounds ridiculous but that’s just my rules.

Am I being ridiculous?