Final answer:
The girl refuses to marry Mattsson due to an absence of love and the quest for genuine happiness, which is affirmed by literature as being more vital than convenience, duty, or social expectations.
Step-by-step explanation:
The girl does not want to marry Mattsson in 'His Mother's Portrait' due to a lack of affection and personal fulfillment. Literature often explores themes of love, duty, and personal happiness, which are evident in the excerpts relating to different characters' reluctance to marry despite societal or personal pressures. Reasons for refusal include being born into a limited situation, lacking love, a duty to adhere to religious beliefs, concerns about social and financial status, and simply not finding interest in the person matching one of the family portraits.
Marrying for love is a common theme in literature and is often depicted as more virtuous and fulfilling than marrying for convenience, duty, or social status. The excerpts demonstrate this through the various dilemmas faced by the characters, which point to a universal truth that genuine happiness often stems from authenticity and true emotional connection.