The PIN you set in the Roku account only affects The Roku Channel. If you or she uses other apps it won't have an effect.
It's not clear what her email password has to do with anything. I assume her TV is linked to a Roku account that you control and the email address displayed under Settings->System->About is yours.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.