Would you find it strange if a 12 year old girl wanted to hangout with your 5 year old?

My son made a friend on the bus. Although I’m thrilled I find it a little strange.. the 12 year old is so naughty. She’s always getting him into trouble. He draws her pictures and she tears them up. Every other day they are friends or fighting. She taught him some swear words. She’s been telling him about her boyfriend and asking which lipstick color my son likes better on her. They get split up by the bus driver a lot it seems. She asked him if she can come over to play sometime. I said when the weather is better, maybe outside. Am I crazy? I don’t want him to mature too fast by this girls words or actions. I don’t see how a 12 year old would want to hangout with a 5 year old. 😣