can I have more than one phone on my Apple ID?

You can have multiple devices (up to 10) signed in to one Apple ID, however, AppleIDs should not be shared with different people as that merges everything on a device with other devices using the same Apple ID, Including calls, messages photos, contacts etc.. You do not need to share an Apple ID to share your location.

Your mom should in fact have her own Apple ID, you are then free to share your location with each other.

See here: How to create a new Apple ID - Apple Support

and here: Share your location with your family - Apple Support

You can have 10 devices/computers linked to one Apple ID. There is a limit of 5 computers.

It would be best if you each had your own Apple ID so that your data doesn't get mixed together. You can use the Find Friends app on older IOS versions or the Find My app on newer IOS versions to share your location.

To create a new ID for her see below. Also she can set up Family Sharing so you can share purchases.

Apple ID - create a new.      

Apple ID – Create         

Family Sharing.         

Family Sharing - Set up.        

If she has your ID on her phone, when changing to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. Also set up Family Sharing between the IDs to keep access to your apps/purchases. 

How to switch Apple IDs on your iPhone or iPad.      

How to transfer all files from one iCloud account to another.        

What to do after you change your Apple ID or password - Apple Support.