What's the right age to teach your teen to use deodorant?

As soon as they experience the growth of hair on their body parts. (pubic hair). My bother's daughter is 13, and she has got hair in her armpits now, but neither her mom or dad have taught her to use deodorant, and the sad part is, that she really has a strong body odour. I have gifted her deodorant but she doesn't use it everyday but sometimes. Only, if parents teach children the importance of these things, children would be able to save themselves from embarrassment.