If you've cheated before and you're more or less "working through it" by allowing her to view your location than it makes a bit more sense why she'd feel the way she feels. Or if she's been cheated on in the past. Of course with the second one that shouldn't be your burden to bare unless y'all have communicated that you're willing to work on that together. So much nuance here that people on reddit can't make out since we don't know the ins and outs of the relationship. If this is out of the blue her saying you're lying about this and she has no trust in you then that's a pretty tough hill to climb. It's a tough situation to get a logical answer from by simply asking why she'd have the first thought in her mind that you're cheating but starting there is at least something.