Q: how to deleate music withought deleating it from a joint acount

Hello, ashes154. 

Thank you for visiting Apple Support Communities. 

There are a couple ways you can remove her music.  If all of your music has been purchased via the iTunes Store, you can delete the entire music library and download it again via the past purchases section in iTunes.

How to delete content you've downloaded from the iTunes Store, App Store, iBooks Store, or Mac App Store

http://support.apple.com/kb/HT5772

Download past purchases

http://support.apple.com/kb/HT2519

The other option would be to locate every song purchased by her Apple ID and delete it manually. 

• Select a purchased song in your library and choose File > Get Info.
• Click the Summary tab. Note the Account Name that appears in the list. This is the account name (Apple ID) you'll need to use when authorizing your computer to play this purchase.

iTunes 11 for Windows: Edit song and CD information

http://support.apple.com/kb/PH12360

Cheers,

Jason H.