Is it bad to sleep in a room next to a man?

My sister was looking to move into an apartment with a roomate. In the tiny apartment, there were just 2 rooms and a bathroom. The two bedrooms were literally inches away from each other, just right next to each other. There were doors but no locks. The male roomate asked my sister if she minded sleeping right next door to a man every night. She said she didn't mind. My mom said it was a bad idea but my sister says she doesn't mind. She doesn't think anything bad will happen. The guy was also super nice and seemed normal.
Is it bad to sleep in a room next to a man?
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