Disconnecting a account

Assistance needed??

I recently sold my old ( 2007) apple laptop, the seller contacted me letting me know that he is unable to log on because my daughter created her own account and he is only able to log on as a guest. I do not want to give him my daughters password because I fear that all her content (passwords, pictures, even credit card info) may be on her apple account. Is there a way for me to disconnect and delete all her apple account info without doing it from the actual laptop I sold?