I searched the text up to Ch 12, looking for instances of the following words when they applied to Anne:

amused, enjoy, happy, laugh, pleasure, smile

Instances in the earlier chapters are sparse and equivocal:

Ch6. Anne's playing gives pleasure only to herself. Mr and Mrs Musgrove's indifference to any but their daughters' playing gives Anne much more pleasure for their sakes, than mortification for her own.

Ch7. Wentworth's comment that she is so altered that he would not have known her must make her happier.

Ch8. Anne suppresses a smile at the irony of Mr's Musgroves fond regrets about her unloved son Richard.

Ch10. Walking to Winthrop, her pleasure in the walk must arise from the exercise and the day...etc Driving home with the Crofts, Anne feels some amusement at their style of driving,

The mood shifts in Ch11, when the ingenious contrivances and nice arrangements of the Harvilles' little home are "more than amusing to Anne". Also, she “could not but be amused at the idea of her coming to Lyme to preach patience” to Harville.

Ch12 opens with Anne's walk to the sea with Henrietta, in which
"They praised the morning; gloried in the sea; sympathized in the delight of the fresh-feeling breeze --

The up-beat mood persists:

"Anne smiled more than once to herself" during Henrietta's speech about Dr Shirley employing a curate.

"Anne was amused by Henrietta's manner of being grateful, and amused also that the course of events and the new interests of Henrietta's views should have placed (Lady Russell) at all in favour with any of the Musgrove family."

Then follows the walk when William Elliot admires her, alerting Wentworth to her returning beauty, and a second encounter with Mr Elliot. Even Henrietta's accident has positive effects for Anne:

"You will stay, I am sure; you will stay and nurse her," cried he, turning to her and speaking with a glow, and yet a gentleness, which seemed almost restoring the past. She coloured deeply, and he recollected himself and moved away. She expressed herself most willing, ready, happy to remain. " (I love this moment BTW.)

"Captain Benwick was most considerately attentive to her; and, united as they all seemed by the distress of the day, she felt an increasing degree of good-will towards him, and a pleasure even in thinking that it might, perhaps, be the occasion of continuing their acquaintance."

"But the remembrance of the appeal remained a pleasure to her -- as a proof of friendship, and of deference for her judgment, a great pleasure; and when it became a sort of parting proof, its value did not lessen".