Sophy is presented as an intricate, worthy character through the metaphor of her beautiful woven hair. One lack she may have as a character is a low emotional level: she doesn't seem to get very emotional about life's normal events. When she accepts Sam's proposal in her youth, she comments to Vicar Twycott that she isn't all that enthused about her engagement to marry:
'Well--do you want to marry?'
'Not much. But it would be a home for me.
The narrator expresses that she has a similar level of emotional reaction when she sees Sam for the first time after being widowed. The narrator tells us that while she had thought of Sam from time to time over the course of the years, she had not thought of him with deep emotion; she just wondered if she might have been happier had she patched up their quarrel and married Sam after all.
She had occasionally thought of [Sam], .... She had not thought of him passionately, ...
The one real negative trait we learn of is that while she is virtuous, it seems that once her good opinion is lost, it remains lost. It seems this is why she never tries to mend her quarrel with Sam (or maybe the quarrel was of such a nature that it could not be mended or patched up, which then elevates her character rather than lowering it).
One thing Sophy certainly is not, she is not the bearer of the responsibility for her own life's sorrow. At all points, the narrator paints Sophy as being true to her name: Sophy means wisdom. She makes a good choice to marry based on her best information and her circumstances. There is never any indication that she is materially unhappy or displeased with her husband. Her sorrow is that she embarrasses her gentleman son with her village ways.
Through Sophy's characterization and name symbolism, the narrator makes it clear that Vicar Twycott and Randolph are the responsible parties for Sophy's misery: Twy-cott means two with hard hearts.
she seemed to be pining her heart away. 'Why mayn't I say to Sam that I'll marry him? Why mayn't I?' she would murmur plaintively to herself ...