Would you let your young teen stay at her bfs?

I don't get how some mums let their daughters stay at the bfs house til gone really late yet won't just let them stay!? Why u thinking she will have sex if she stays, she probably already did since being there for so long.

What do you women think? Is that just silly and would you let your daughter stay over? And why

*personally I wouldn't but I wouldn't let her (if I had one) stay late either, I'd rather he slept at ours until I get to know him well*