At what age do you let your kids stay out a bit later?

[Sevillian]

Our daughter who is only 8 years old and to us still a kid has recently taken up with a new friend who stays in the same street. She is a bit older than our daughter although not much but she does hang around with some of the older kids around 11-12 years old. What with it being winter and it getting darker a lot earlier I reckon around 7pm is the latest we should be letting her out. However she is not happy with this as the other kids are staying out a bit later and obviously we don't want to embarass her in front of her friends. We have tried to encourage her to play in or around her own garden and then maybe allow her a little extra time however her friends don't always want to do this and our daughter gets frustrated when called in and feels we are showing her up. What would all you say is a fair time? She never ventures further than our own street to be fair but as parents we will always worry about her.