Single male, 45, should I let my daughter's (14) female friend (14) stay overnight?

Just want some opinions. She has her friends over during the day, but I'm being nagged to let one of them stay overnight. I don't really feel comfortable with it, being a single male. I've said no at the moment but now she's sulking!

Am I overthinking this?

The same friend wanted to stay over a few weeks back, and her father apparently said no at the time because he didn't really know me, which is fair enough.