Not sure what you're wanting to do but you have the option of adding usage controls to your account (can't recall the monthly fee but you can look in My Verizon for that). You can use Find My iPhone if you're trying to track the location.
If you turn on track my phone in the iCloud settings you can track the location of any devise if you know the apple account and password for from the iCloud web page or the find my iPhone app
If you use a single iCloud account, you can track her phone using find my iPhone.
You can also use find my friends if you use different iTunes account.
You can also use Google latitude