first i would freek out. then i would ask him: "why are Du at my house?" then have a chat over with him go with the flo i guss (if i don't faint at first sight!)
I woud say ohhh miiiiii Goddddd I can't believe justin bieber is in my house lukin at me ahh thn id faint and then he would help me to the couch and then he would ask oh my god r u all rite and then I would say yes he's like would u like a ice pack and thn i would say yes plz and then he would say would U like to go to my house and then I would say yes plz and then he would take me to his house and then he would give me his number and then he would lay me down in his bett then say do u wana make some magic and id be like SURE!!!!!!!!!