Has she had access to your phone and knows how to use location sharing? Or have a parental monitor app installed?
Test the chime is definitely triggered by your phone. Turn it off turn it on every 5 minutes or ten minutes.
or even better…
Turn your phone off 30 minutes before you know she is not active on her phone, say, when she has come round your place for a dinner date. Say “both of you leave the phones in the kitchen” ( yours off ) then when getting the desert or drinks, coffee, what ever, turn your phone on while looking at the screen of her phone to see if a notification pops up.
Another question is the why. If it is location based either she doesn’t trust you (what have you done to evoke this response?) or she’s doing something and she wants to know for sure you are out of the way while she does it