Eco isn’t a Mode. The car will automatically go to HV Mode once EV range has been used. In other words, you don’t even need to “switch” to HV.
Higher speeds on the interstate will yield fewer EV miles than slower speeds. The interstate would be the place to use HV Mode. After rereading your remarkable sentence and adding my own punctuation marks, I’ve concluded that your wife has ~48 miles of freeway and 32 miles of secondary roads on her round trip. If the vehicle is being operated in temperatures above, 50-60F, it should be able to cover more than 32 miles in EV. In that case, it wouldn’t be necessary to drive the entire 48 freeway miles in HV, if one of your goals is to fully utilize EV range. She’ll have to experiment with the amount of miles driven in HV.
A number of owners prefer to engage “Sport”, whether in EV or HV, which provides peppy acceleration with less input. It also allows the paddle regen setting to stay set for the entire drive. Keep in mind, there is no way to “lock in” EV Mode. If sufficient acceleration is called for, the ICE will come on.
And, please consider adding a few periods in future posts.