If they self-diagnosed her as bipolar, it makes no sense. If SW had been diagnosed by a doctor (and CW relayed it to his parents), but did not take the medication, it is a totally different stories. Truth is, we don't know, and never shall know. In general, 25% of women will have at least one episode of depression in their lifetme, so the diagnosis of affective disorder is neither rare nor stigmatizing.
I see a couple of things in SW that raise certain flags, but I see the same in CW. Clearly, the family could not balance the budget, at the end, their budget was abysmal. Also, falling for the promise of making big money on some lifestyle product might be the symptom of something, but not necessarily illness. Maybe, "gullible" should be the word?
And then, Shanann creates online "magic story" of their family, and Chris creates his own "magic story", that of all-encompassing love. Both stories are incredibly far from the truth. Hers, ends up in death of herself and the kids, his, ends up in murder and prison.
From this, I can only conclude that Shanann might have had emotional problems, but hers were nothing compared to Chris's ones.