Are my wife and I wrong for insisting our 15 year old female niece and her boyfriend sleep separately while at our house for thanks giving?

So here is the story, I have 8 nieces and nephews and their parents staying in my home for thanks giving next week. This a mounts to 3 full families. I have two older nieces (aged 15). One has a boyfriend that she is bringing with her, which I'm OK with for the most part. I just draw the line with the sharing a bed and being behind closed doors together.. Not in my home. She has chosen to call my wife and I hateful, and fascists. Her parents support our choice thankfully.

Am I in the wrong here?
Updates
+1 y
To that anonymous user.. I removed your comments. Do your self a favor, spread your pedo rhetoric elsewhere.
Are my wife and I wrong for insisting our 15 year old female niece and her boyfriend sleep separately while at our house for thanks giving?
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