The little cabins at KOA are nice, but based on your parameters, you should know that they are just a little one room cabin with a TV and beds. The bath house must still be used for shower and potty runs. We stayed there a couple years ago, nice enough, but might not be what your wife is looking for. Panther Valley is nice, but I suspect it may be booked up already, they have a web site you could google them and double check. Edit: just checked, they all booked up.
Hot Springs proper is only about 15-20 minute drive from the park so the hotels aren't too far away, as long as you don't enjoy the band or
@Land Speeder's jar collection too much