Wife is 4'11"..
Can she touch ground while sitting.
Yippie toe touch ok
Easiest way to know is to measure her inseam and then use this sizing chart from Rad Power Bikes, it's quite helpful: https://bit.ly/3pz8MGI
To determine your bike frame size, you need to know your inseam measurements first. When you are trying to measure your inseam for bike size, you can start by browsing through the inseam measurement chart with its respective bike sizes to find your future bike!