10 year old sexual curiosity

I just learned that my 10 year old daughter touched her 8 year old friends (also a girl) private parts.  The girls mother is freaking out.  She said it happened one other time, but she never told me about it.  I spoke with my daughter and explained that she should not be touching anyone there nor should she let anyone touch her there.  She was embarrassed and said she would not do it again.  The girls mother thinks I need to get helf for my daughter.  Is this behavior abnormal at this age?