Anyone remember enough about the plot to know why she'd react like that? I sure don't
My guess is she thinks Zeolith asked "his master" for help since she wants the grand prince staff of "something" as it was used by a [Great Sage] (not sure if it was the one, meaning 400 years ago) whom was an elf, thus she wants to return it to her people (the elves).
However, when she told Zeolith, she also said she would pledge her remaining lifetime to the one who gives her the staff of "something". Aside from the hints she has been dropping in various chapters, she
might have changed her feelings towards Zeolith from
like to
love.
Thus I think, she thinks Zeolith has implicitly declared
his love for she by having "his master" win the tournament and finally pass the staff of "something". Whether that pledge means a permanent slave [crest] or marriage, is another thing.