I have music on my MAC from CDs that I scanned. How do I share with a second iPhone?

You would have to sync the 2nd iPhone with your Mac. If she has her own computer you can also share the music library with her computer, and she can then sync her phone to it ➡️ Use Home Sharing to share media from a computer to other devices - Apple Support

Another option is iTunes Match, which uploads your CD images to Apple’s cloud, when they become part of your music library that can be shared with Family Sharing ➡️ Subscribe to iTunes Match - Apple Support. Note that this link “encourages” you to join Apple Music, but you don’t have to.

Sync the music from the computer to the phone. Start here: https://support.apple.com/en-us/HT201253

See the Home Sharing link I posted. You can share your library with iTunes or the Music app on her Mac.

And iTunes match will also work if your phones are linked with Family Sharing ➡️ What is Family Sharing? - Apple Support

she does not have to use your Apple ID for either of these.