1. Not sure, since I use wireless.

2. There should be an adjustment for tire diameter, and you can change the setting a bit on either yours or hers to make them come out reasonably close. Ride the same 10 miles exactly and if it comes up like you say (9.85 for her) then her wheel diameter reading is 1.5% larger than yours. Change her setting by 1.5% and they should be sorta close. Hubby and I went through this on our bikes and we thought we had it down to a science. Then they'd still be different at the end of a 20 mile ride. I started ignoring it, figuring I had a lot more important things to worry about, like whether or not he'd be taking me out to dinner later on.