My DCs have 'the normal teenage life'. It's just that 'the normal teenage life' where we live does not include the sort of early sex that some here think of as normal. What is normal here is the sort of homework and sports and extra curriculars the OP's DD enjoys.
I am not talking about physical maturation of secondary sexual characteristics. I am talking about brain development and its impact on emotional, psychological and cognitive development. I have not forgotten how teens think. I believe it is precisely because there are serious flaws in teen 'thinking' that the job of parents to save them from themselves by steering them away from behaviour and activities that can have very serious consequences.
The brain does not mature physically until the early 20s, lagging far behind the rest of physical development, and its physical immaturity accounts for a lot of the cognitive and emotional immaturity that most people (but apparently not you, Fleurdelise) observe in teens. According to you, a child can accordion almost a whole decade of social-emotional, psychological and cognitive development in the space of maybe three years. Perhaps you believe that young teens who are sexually active have somehow managed to develop super brains of some sort? They do not 'start earlier'
on brain development.
People whose cognitive development is still ongoing lack good judgement. Anticipating consequences of their actions can pose a challenge. They can be impulsive, hasty and even selfish. There is a reason 14 year olds do not get to vote or drive and why it is recommended that they not be employed as babysitters.
Brain development is also responsible for the ability to regulate emotion, and until the brain is fully developed teens can also have difficulty putting events and perceptions in proper perspective. Regulation of emotions and moods is another important offshoot of brain development. Sex hormones that are new to the body further complicate this element of the maturation process.
I think it is realistic for parents to take all of that into account when dealing with teens and not be carried away by warm and fuzzy sentimentality along the lines of 'Don't dismiss love at 14 as "childish"'. I look to statistics and actual facts of real life and not to fairy tales for inspiration and I hope to impart that approach to my DCs too.
And why is it fine in our society to be proud that our kids are academically advanced but be horrified that they dare trying to be emotionally and physically advanced
Because the job of teens is to prepare themselves for adulthood, and adulthood includes holding down a job that will support them and their future families and allow them to live independently.
We are concerned when we see them engaging in risk-taking because we are adults and we can see where many risks lead. We understand that they are immature and incapable of taking all factors into proper account when making decisions and therefore we try to keep them on a path that will end up well for them and not result in enormous and unnecessary struggle and the loss of most of what really is 'normal teen life' -- widening your social circle, deepening your friendships, going to parties, enjoying hobbies or fitness, watching tv or browsing youtube or reading without having to change a nappy/feed/settle a baby to sleep, sleep in on a Saturday morning, make impromptu trips to the beach, see friends at the cinema or head out shopping without having to scramble for babysitters for your toddler, at 17.
'first love is special'
"Gobsmacked" is not adequate for the attitude of which this is emblamatic.