Well not quite alone, but please tell me AIBU and must bring her in immediately!
She is four. We live in a cul de sac type street, so there is very little traffic. She is with dd1 (8), dd1's friend (10) and her own friend (also four).
She is playing in her friend's front garden/palasade type thing. It's directly opposite our house. We are checking on her every five/ten minutes, as is friend's mum.
Friend has older siblings who are in and out almost constantly and one older sibling (13) who is also playing out the front but up and down the road.
It is a bad idea, yes?