I'm glad you decided to get rid of Limewire. There are legitimate uses for it, but it's rarely used for those purposes. Same with BitTorrent - there are quite a few honest, legitimate users of BT who see it as a great way to (legally) exchange large files. But most torrents are for pirated items.
Until you add individual family member accounts to your Mac (which, BTW, is trivially easy to do in System Preferences...->Accounts), you might seriously want to consider creating an admin account and making the 'standard' account non-admin. It'll take three minutes, and it will add some security.
As far as changing the admin password on the current account: unfortunately, one of the advantages to Mac use is that many apps don't get 'installed', and so there isn't a need for an admin password to install/use them. Therefore, it's hard to ensure that your daughter doesn't download/use other apps. Setting up a separate, limited account will help, but it's hard to be sure without being a complete ogre about it. If you set up a separate account for her, and lock down most of the public folders, you could search every few days for newly created files above a certain size and see if any are apps.
Good luck with it.
As far as your question about the e-versions of your CDs: technically, maybe you should dump the copied versions if you sell the CDs. However, no one will ever prosecute you for keeping them. If you sell the equipment with the copies still intact, then, maybe, you might possibly have something to be worried about. Very, very, very unlikely, but maybe. Keeping the copies at home on your equipment after you rip and then sell/trade the CDs isn't going to get you into any trouble, and I'm not even sure that it's technically illegal.