I beleive it would be cheaper for her to fly into Orlando (MCO). For your convienece Vero or Melbourne would be the other options. Remember it is about two hours from MCO to VB.
The major airports are Orlando or West Palm Beach. Some airlines also have flights into Melbourne which is the closest but you'd want to check costs and whether the flights are direct or not. The Vero airport is for private aircraft only.
We flew into Melbourne when we brought our mom along. Musch smaller but really nice airport and not so overwhelming for an older person. Only 30 minutes away from Vero I think. Our prices from Oklahoma were comparable to flying to Orlando.
Tigger it is a little bit faster to come from West Palm and the ride is more interesting. If Vero were the only destination, West Palm would be the choice over Orlando.