How do I keep Norton Family on an Android Phone after being factory reset?

The situation is that my niece has an android phone that was bought from China (with her own money), and if it matters, the only information it gives is the model is an X6 Pro (no brand) running Android 4.4, unlocked 3G/GSM AT&T phone. My mom has temporary custody of her, so there are some things I don't feel as comfortable with (I.E. taking away the phone completely).

My question would be, is there any way to make sure the app stays on the phone and linked to my account after a factory reset? From what I found is, even if i set the app as a System App (by rooting the phone), it could still delete the app data, which means I would have to login to get Norton Family to work (this would be a problem).

What have others done to get around this issue with resetting to factory?  My niece doesn't have a problem reinstalling all of her apps, as long as we can't track anything she's doing or lock her out of her phone. This would be the best option as well, since if we have control over her phone (bypassing any obstacles) we can set the rules easier and keep her from staying up late at night.

I tend to over explain things, so If anything isn't clear, let me know.