Now you are stretching to make your point. If you told her the Packer's are "heavily favored", "big underdogs" or "10 point favorites" she would understand all three of those. If you told her "the Packers have a minus 10 point spread today" she would not know what that means or even how it is used.
Reading comprehension is a good skill to have. Here is what I said "I believe we are still a 2 touchdown underdog at home." So, she would understand "10 point favorites", but not "2 touchdown underdog"? Somehow, you stretched that into a discussion of Vegas betting lines, not me, to prove a point that is untenable.
Cheers.