Well some of those GM posts are funny in that they reach so far to prove their point.
About doubles, honestly, it's hard for me to see how much incremental benefit her singles game would get from training for and playing doubles vs. training for singles and strengthening her net game to be passable if not great.
Also, if she were to play doubles, she would do it seriously and not just for shits and giggles so she would likely want someone who takes doubles seriously rather than one-offs like partnering with Petra or Woz for the star-power-like teams. I see the latter as a waste of time and something she can do in exhibitions. In the former, if she were to play with a player who takes doubles seriously, like GS winner
Lena V (my pick for her doubles partner) or Petrova (just for the LOLs), I would actually feel bad for her partner because it would be better for her partner to have someone who takes doubles seriously, is good at it, and can work together to win the doubles title. Martha would be dead weight there. So no doubles for me.