Where did all my mom's data go? and how can I prevent a reoccurence?

She has a Galaxy S7 Edge with 2GB of data monthly. Android OS (Beaming Service?) burned through 1.54GB in 3-4 days. What should I be looking for next time I get a chance to check her device? I know android phones well enough to be able to dig around in the settings and permissions but i'm not really savvy enough to know or figure out wtf happened.

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