Since this is for SWMBO, I'll suggest a feature to look for.
Auto power on/off. Get one that automatically turns on when you turn on the TV, whether it's by detecting the audio-in signal or "learning" your TV remote. Otherwise she'll have to use 2 remotes... one for the TV and another for the soundbar.
It's ok if you have to use the soundbar remote for setup and various configuration functions. But for simple on/off and volume, she may not be happy if she has to use two. (I know because I got one for my mother.)