IMessaging, different devices and users

Hello All

In summary, we have a number of devices all linked to one Apple account.

My daughter uses Imessaging on her Ipod, using the main Apple ID/account and my email address in the settings section.

Our problem is that when I enabled Imessaging on my IPhone, my daughter started getting all messages sent to me, including those sent via Mobile phone messaging (i.e. standard 2G/3G texts).

When I removed my email address from the settings on her Ipod, she stopped receiving messages altogether.

I don't want to set her up with an Apple ID as I want to control what is bought/downloaded, so how should we configure each device to ensure she gets the messages only intended for her and I get those only intended for me?

Many thanks!