How did Mercy react to becoming sick in The Witch of Blackbird Pond?

A
reader should check in chapter 17 for solid textual evidence regarding this question. Readers
are told right at the start of the chapter that Kit is healing nicely, and she asks Mercy for
some help. Kit is shocked to discover that Mercy can't answer because Mercy is hit with a
coughing fit that doubles her over. It is almost...