Q: will deactivating my daughters iPhone from my iTunes account cause her to lose music?

bb1754 wrote:

 

will deactivating my daughters iPhone from my iTunes account cause her to lose music?

Do you or she have a backup copy of all the song files?

BB,

If she has copies of your songs in her own iTunes library, and she syncs her iPhone to that library, she will still have them.

If she needs to download fresh copies, she will not be able to since it requires access to your account.  However, you can solve that by putting her new ID and your ID together via Family Sharing:

Family Sharing - Apple Support