I would allow it, I think - maybe with a door open policy - at that age I just wanted to be away from my family (sooo embarrassing!) and have the feeling of privacy.
Speaking as someone with a toddler who thinks a lot about what I'd like to change about my teen years, I wonder if OP you would indulge this tangent, to ass that I would also talk to my daughter about things like, not having to do anything to make a boy like you, and making sure she feels comfortable, and what consent is, and that attention feels nice but people can change and turn nasty, so it's worth being a little circumspect in who you get vulnerable with.
Oh, it'd be superbly embarrassing, I'm sure, and as a 14 year old I would have grimaced and FLED if my mum had tried to tell me that snogging and groping was fine, but no one should push me around and it is ok to be a 'prude' (or indeed a slut) if I wanted - and what I wanted mattered as much as whatever my boyfriend wanted. I would have crumbled into the floor with embarrassment. But I absolutely needed to hear it, and I didn't, until years later. My parents did the 'mechanics' sex talk, as little as they thought they could get away with. I wish they'd done the 'feelings' part too. I suppose I'm thinking of something like the dad in 'Glee' did so sweetly (transcript here.)
But my mum couldn't bring herself to tell me about sex really, apart from 'wait till you're married!' - which was wildly unrealistic for a teenager in the nineties!
of course, these are just your DD's mates, and this IS a big old tangent. But thank you for letting me litter your thread with it 