I don't understand the thought that there's anything like Munchausen Syndrome displayed by SB. There are two forms: Munchausen syndrome and Munchausen syndrome by proxy. Both involve either faking or deliberately inducing conditions requiring medical attention, in order to get medical attention and the general attention and sympathy which ordinarily accompanies illness serious enough to require medical attention. The "plain" Munchausen syndrome is when the person makes themselves the patient, and the "by proxy" Munchausen syndrome is when the person makes some other person (who is not knowingly cooperating in the fraud) the patient -- in most cases, the proxy is a child because 1) young children aren't able to understand everything that's going on and tell other people, and 2) the sympathy and attention and tangible assistance customarily rendered to a parent of a very sick child is huge draw to someone inclined towards this sort of thing.
There's no evidence that SB has evidence faked or caused medical problems in herself or others, and then sought medical attention for it. She brutally abused a little girl, but that wasn't discovered until an big investigation was launched into the disappearance of the girl's sibling, with SB as a suspect. It's not like SB was brutalizing the little girl and constantly running her to the ER claiming accidents or that somebody else had hurt her. She concealed the abuse for as long as she could. And in the case of Shannon, there's no evidence that anybody had ever faked or caused illness or injury to her. Making a false complaint of child abuse certainly doesn't qualify as Munchausen by proxy -- if she actually inflicted the abuse, and then sought medical attention for it, claiming somebody else did it, that *might* qualify as some sort of Munchausen by proxy, if her chief purpose was to draw attention and sympathy to herself.