Define:love why don't you . Love can be expressed in different ways and be caught in different perspectives, the best thing to do is to respect those perspectives and forms of expression.
A teenager loves his dog. That's wrong?
A teenager loves his parents. that's wrong?
A teenager loves his girlfriend, and they grow up, get married and die at an old age. that's wrong?
Where have I said that it is wrong?
Loving your pet is a null and stupid argument. I only believe their love if that Dog saved their life when they were a child. THAT is real love. And that occurs often.
Someone who loves their parents isn't debatable. You're with them for all your life. Obviously you would love them, since you have been with them since you were just a baby.
Now the girlfriend part. THIS is something that is debatable. It is bullshit if the teenager says they love their girlfriend, unless they dated for years. If it's less then that, then it's just pure desire and lust. Besides, IT IS VERY,VERY RARE to have two people be together until they die. It takes serious commitment. Many people aren't competent enough to commit.