This is a difficult question to answer, because the final chapter does not tell us directly the opinions of Hester on adultery and betrayal. However, the way in which Hester suddenly reappears after a long period of absence, and the way in which she still chooses to bear the Scarlet "A" on her bosom perhaps indicates that she feels that she needs to bear it as a result of her sin of adultery and betrayal. The scarlet letter though has changed in the way that others view it now, and it has lost its stigma. Another section of the final chapter that you might find interesting to analyse is where Hester is buried:
And, after many, many years, a new grave was delved, near an old and sunken one, in that burial ground beside which King's Chapel has since been build. It was near that old and sunken grave, yet with a space between, as if the dust of the two sleepers had no right to mingle. Yet one tombstone served for both.
Clearly, we can assume that the other grave is that of Dimmesdale, and the way in which they are separated seems to suggest that the novel is not approving of adultery completely, but the fact that these two graves share one tombstone indicates that, in death at least, Dimmesdale and Hester can be united in a way that they never could be during their lives. The clues that the novel gives us therefore suggests that Hester Prynne believes that adultery and betrayal is not justified.