Find My Friends App.. Girlfriend was able to cheat anyway.

I’ve been with my girlfriend for a few years now. Toward the begging in good of our relationship, she cheated. We worked thru it.. She, being the cheater, was very paranoid of me and what I was doing. I, who had nothing to hide, decided we should use the Find My Friends app so there was never a question as to where we were. We could check out each other’s locations whenever we felt the need. For a couple years we used it and it was never an issue. In fact, we used it in very healthy ways... Recently she has started to act very strange and paranoid about me and my location.. I’ve never cheated and try to be completely transparent with her. To me, this was an indication that she was up to no good.. That was why she was all of a sudden worried about me again. Her affair years ago was with a co-worker. Recently I noticed that all of a sudden he is a friend of hers again on social media. I am almost positive that she’s messing around again. Her location says she’s in her office but can’t text or call for huge 3-4 hour chunks of time during the day. She has the freedom to come and go at work as she pleases..

My main question is how she could be leaving with the Find My Friends location showing that she’s always in her office. I know she would never leave her phone at work.. She has an iPad.. Could she be changing the device on Find My Friends to the iPad and take her phone without it showing her location with her phone? Just leave the iPad in her office? Is something like that hat possible?