In game shop issue

When my friend goes in to the in game shop to buy coins using her Google play balance it only comes up with my account details which is a pain as she has 12.45 in her play account and I have 0.45 and its my account it should show her details.
I once got her some coin with my payment details but now we want it to show her Google account and be linked to her Google play balance.
Does any one know and to do this?

You should be able to just delete your card info off her game.