Is life360 battery accurate?

my sister and i have life360 on our phones so we can see where we are, specially when we go work. mostly we have it bc she works until late, almost night.
her phone is an iphone 6, it’s old and she has tons of apps and stuff. sometimes the app says she has 99% battery, and then one minute later she’s on 75% (for example). it says “last updated now” all the time, so it’s not that it didn’t update. and again, then i go check again and the battery keeps going down or all of a sudden it stops going down.
does the app not work right? or she’s just simply using the phone?
Is life360 battery accurate?
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