My best friend has an old iPhone 5 she use to play pokemon on. For Christmas I bought her an android so she can play again but we don't know how to move her account over. Other words old iPhone to new android.
It depends on how she created her account. Sadly, if it wasn't through her email or Facebook or Pokémon account, but through her Apple ID, you can't. If it was through the other ways, all she would have to do is normally log in with Facebook/email/Pokémon trainer club account.
Just open Pokémon go settings on iPhone, CONNECT the account to Facebook and on Android, sign in via Facebook. I don't know other way.