Help, I dont know what to do?!!!?

So my friend has a dilema and I want to come up with plan to save her (literraly). Ok, so we have a friend who has been obsessed with getting a girl and is hitting on my friend. She has no interest in him because she gave him a chance before and he was immature. Now he visits her house constantly to the point where all the family is encouraging her to date him. She doubtful about giving him a chance and has made it clear that she doe s not want to be romantically involve with him because he is immature. She want to let him know she does not want anything with him but we have known him since we were kids so she doest want to hurt his feelings but if she tells him otherwise he will overreact. What should she do?Please think about your answer she really needs a good suggestion!!!