This is not really about English, but rather more about how the role of women has been historically perceived in certain European societies. There is a kind of romantic notion of certain women who acted as as healers by collecting natural remedies and dispensing advice, in order to minister to the sick and injured who would otherwise have had no access to medical services.
The author is saying that one of the consequences of the Scientific Revolution is that these women were often persecuted, and in some cases killed (possibly for the crime of "witchcraft"). The end result is that women were driven from their traditional role as the primary "healer" in a community (presumably to be replaced by male physicians).
In modern usage the term "healer" can apply to anyone who cures illness or injury; however, it is often used to distinguish those who practice non-traditional methods of healing (such as "energy workers" or purveyors of "natural/herbal remedies") from more traditional professions (such as doctors or nurses). Non-traditional healers would also include "faith healers" who claim to cure by invoking divine intervention, and who exist in almost every religion.
To some extent, this modern use of "healer" refers to the historical definition of "folk medicine", to imply that sometimes those older, traditional methods are more effective than modern medical therapies.
Side note: I call this a "romantic notion" because people who speak positively of traditional healers often cherry-pick their medically valid advice (such as using willow bark as an analgesic), and ignore the kind of "folk wisdom" that was bizarre, ineffective, and occasionally harmful (of which many have been documented).
This isn't to imply that educated physicians were much better. Up to the end of the 19th century, for example, bloodletting was considered a medically valid way to "treat" almost any disease (despite the fact that it not-infrequently killed the patient).
Again, this is more about history than language, but it may help to give some context to the authors use of "healer" in this context.