The only thing worse than a cheap gas grill is.... well nothing. I hated gas grills for years because I only owned cheap ones. Trying to cook chicken on a cheap gas grill is like trying to toast marshmallows in a forest fire, It wasn't until I invested some money that I finally leaned exactly what you are telling your sister because you definitely get what you pay for when it comes to gas grills. If the family thinks the Genesis is too much and if mom doesn't want to do anything fancy, you might want to look at a Q300 or Q320 although the Genesis is definitely a much better grill.
WSM, 2 -Performers, 2-OTG, SJG mini WSM, Summit 420, Q100, KJ Classic, KJ Jr, and Schwenkgrill