Reverse the genders and it applies to boys too. I am the bad cop and Mrs Nick is the good cop. It has given us a lot of trouble
That is how it works. When you have "Single parent" (how I hate that expression) households then there is no partner to leaven the mix. Thus Uncle will enjoy a reasonable relationship with daughters but Miss D will struggle.
Added to the normal problems you also have a whole generation of teachers and labour politicians (and labour aren't the only ones but they are the ones who have presided for the last 12 years) who specialise in telling children that they have rights, that parents are bad, that the state knows best etc etc.
I am not looking to start an argument about smacking but it didn't happen in my teen years and the only difference I can see is that children nowadays have acquired "rights" without learning about responsibility, nobody wallops them any more, not parents nor teachers. Discipline is the answer but how we get it back I have no idea.