Help! My friend has some of my contacts on her new i-phone. How did this happen?

[bigTillyMint]

Somehow some of my email contacts have appeared on my friend's i-phone. She didn't knowingly do anything to get them, so how could this have happened?

TIA

Are they e-mail contacts? If she has 'reply all' to an email with these contacts also as recipients they they will automatically be added to contacts.

Yes, email contacts. I thought that might be it, but it has never happened to me.

Thanks, I feel relieved that there isn't some terrible virus going round