I also have American and Canadian friends who in their adult years have talked about the stuff that had happened to them at sleepovers at close family friend's houses or close relatives and I don't wish them on anyone. Even though you personally know that friend's parents, there is no guaranty that nothing will happen to your child, every family has their own problems that are not advertised publicly. So what is the point of risking, even that remote chance that something might happen to them when it really wasn't necessary, they can play for few hours and then come home for sleep.
I also have a lot of non Persian friends that don't allow their kids to go for sleepovers. So, I can tell you that this issue is not only an issue for Persians.
I would not let her to go to the house of some friends that I don't have full knowledge of . But close relatives and family friends that I can leave my child with for having fun and play during the day without my present will be OK for a wished sleepover .
I think she will understand/accept better why I disagree with some places when she can have sleepovers for safe and close friends .
I used to stay at my grandparents house too with my other cousins or stay at my cousin's house once in a blue moon, but we don't have that set up here, and I don't feel that close family friends can replace that just because we had it when we were growing up back in Iran.
I agree with Madar#11. I had sleep overs at my cousins house when I was growing up and enjoyed it so much. I don't think being Iranian or American has any thing to do with this, as long as you feel comfortable with the family and you know them well enough to let your child spend the night there. I wouldn't let my child to have sleep over at friends house until they are old enough to understand, may be 9 years old. 5 or 6 is too early even with American culture. I have a teen age girl and a 10 years old girl and they both started to have sleep over parties when they were 9. I feel if they are too young then it would be overwhelming to them also. Sleeping over at grandma's is different, I am talking about friends and other relatives. Also, I think this is a very personal issue and if you don't feel comfortable with your child spending the night then don't let her and explain it to her, why you don't feel comfortable. Kids are very smart and can easily understand logical explanation. Keep in mind that we can't live in a bubble and have to accept some cultural differences and adopt to the culture here and combine it with our moral values otherwise we will have to deal with very unhappy and morally mixed up children. I feel you have to draw the line when it is your principles and do not bend your rules if they are your principals, but we all live in this country and believe in this society (more or less) and need to accept some cultural differences and try to be flexible.