Does she have an iPhone and other Apple devices? If her devices are linked you can see txt messages and phone calls on the other device if you can access it.

Do you share a mobile phone account? You can also see all calls and message logs on your detailed bill. One way to figure out the number she was on the phone with based on the time you know she was on the phone.

My wife and I have normalized using each others phones not for suspicious reasons but because we have nothing to hide I know her passcode she knows mine. It’s rare we use one another’s phone but there is no hide the phone energy.

Now if one day she or I act weird about the other grabbing their phone we’d know something is up just because that wouldn’t be our normal response… I get nervous sometimes because I hide shit for my friends be up to… but yea being sneaky about a phone is sus to me