Absolutely fine Grandad if you want to embarrass your child and be the place they don't want to come for a sleepover.
The genie is not going back in the bag. This is part of teenage life now.
Of course - if there is a history of stupidity, bullying, inappropriate photos then you have to step in on a case by case basis. The important thing is a good close relationship, close enough to report any problems to you without hesitation. Alienating her from her peer group will not help this. -
Learning self regulation is an incredibly important life skill. It teaches us to be responsible for our own actions. One of the MOST important characteristics of a responsible human being.
Learning that going to bed late and being on your phone till midnight chatting with mates, teaches you that you feel like shit the next morning and do badly at school. The only way to change that outcome is to go to sleep earlier. It's not rocket science. 13 yr olds can learn this.
Ultimately it is essential for future life at Uni. It is telling that at DD1 Uni, the ones with the Mums that phone them every morning to wake them up and have a copy of their child's timetable at home - yes, there are parents that do this !! - are the ones from the strict homes with all the 'rules'.
They are also the ones that go back to sleep as soon as they've got mother off the phone .
Carry this through to the world of work. Punctuality is an essential requirement. Having learned to switch the phone off and get enough sleep to get up for work will be the difference between holding down a job or not.
Cyber bullying and sexual grooming , the things we all care about are LEAST likely to happen on a sleepover amongst friends. Much more likely to occur when they are on their own at any time of day.