In Ch. 22, as Lucy is leading up to the whole subject of the engagement, we have this:
"...But if I dared tell you all, you would not be so much surprised. Mrs. Ferrars is certainly nothing to me at present -- but the time may come -- how soon it will come must depend upon herself -- when we may be very intimately connected."
She looked down as she said this, amiably bashful, with only one side glance at her companion to observe its effect on her.
The whole speech was obviously calculated for effect, and the glances prove that it is so.
And then there is this, just a little later on in the same chapter:
"...Everything in such suspense and uncertainty, and seeing him so seldom -- we can hardly meet above twice a-year. I am sure I wonder my heart is not quite broke."
Here she took out her handkerchief; but Elinor did not feel very compassionate.
"Sometimes," continued Lucy, after wiping her eyes, "I think whether it would not be better for us both, to break off the matter entirely." As she said this, she looked directly at her companion.
It's like the whole thing, inlcuding the gestures, the handkerchief, the eye wiping, the glances, all of it has been rehearsed like a play.