Mrs. Trubus (spoiler)

There's a book called Fifty Great American Silent Films, 1912-1920 by Anthony Slide and Edward Wagenknecht featuring a chapter devoted to this film. To quote from the plot synopsis there:

"[Mary Barton] and her lover record the conversations of the criminals, by which means they are brought to justice just in time to wreck the betrothal of the fake reformer's daughter to 'the catch of the season.' The shock kills his wife, estranges his daughter, and leaves him desolate."

That sounds right to me, based on what we see in the film. If Mrs. Trubus had killed herself with poison or in some other way I believe the filmmakers would have indicated that. We're meant to understand that she's so traumatized to discover what kind of man her husband really is, the shock is fatal.