| Quote #1
One point was evident in this; that she had been existing in a suppressed state, and not in one of languor, or stagnation. (1.6.9)
Hardy may have been brushing up for a vocabulary test here, and the distinction between the three adjectives he uses is really important. "Languor" implies that Eustacia is lazy and "stagnation" implies that she is stuck. But "suppressed" suggests that there actually is a lot going on with Eustacia, and that she is tamping it all down. So suppression makes us think that Eustacia may change at some point and unleash all of that emotion she's currently reigning in.
| Quote #2
[S]he yielded herself up to the pull, and stood passively still. When she began to extricate herself it was by turning round and round, and so unwinding the prickly switch. She was in a desponding reverie. (1.6.18)
Hardy creates a really powerful image here of an emo girl twirling herself round and round, or something. But seriously, this imagery gives us great insight into Eustacia's state of mind – actions really do speak louder than words (or dialogue, really) here.
| Quote #3
She went indoors in that peculiar state of misery which is not exactly grief, and which especially attends the dawnings of reason in the latter days of an ill-judged, transient love. To be conscious that the end of the dream is approaching, and yet has not absolutely come, is one of the most wearisome as well as the most curious stages along the course between the beginning of a passion and its end. (2.11.86)
The word choice here really helps emphasize how sad Eustacia's current state is – words like "transient," which means short-lived, and "wearisome" emphasize not just Eustacia's emotional state but also the slow progression of her feelings. This definitely isn't a sudden realization for her.