Wow, too precocious! I'd have to say it is not normal, but that your young lady got curious and took steps to satisfy that curiosity. What she has learned however, cannot be a positive experience. Perhaps 8 year olds shouldn't have cell phones. Were I you, I'd seek some professional counseling on this.

Wholeheartedly agree with the previous answer. I see this as a very serious issue and I would want to know the name of the child who was asking about this topic and asking for both children to be separated at school. Why does an 8 year old girl need an Internet access phone? Last year she would have been 7, I guess when she was looking at unsuitable material on the great grandparents' computer. Who is responsible for supervising this girl and ensuring appropriate parental controls are in place to prevent access to unsuitable information? Is this girl "at risk"?

Wow!  My concern is - why does an 8 year old have a cell phone? Also, why is there no supervision when she uses the internet on the computer?  Perhaps it is time to talk to her and inform her about this issue and that she should not be watching porn.  You could ask the teacher to deal with the subject in a manner that all children benefit from the talk.