Is a daughter considered sinful for not being pleased with the actions of her mother — who raised her and her sisters after their father’s divorce, and refused to help her with her marriage despite having savings, and sold her [the daughter's] jewelry that she had entrusted to her — especially with the presence of harshness within her towards her sick mother, and what should she do about that?

The right of the mother is great, and honoring her is among the most obligatory duties. Regardless of her condition, she has the right to dutifulness and good companionship. Beware of mistreating her or falling short in her rights, and strive to be good to her, for it is one of the greatest causes of success. What you find within yourself towards your mother, if it does not affect your dutifulness to her and your fulfillment of her rights, does not harm you. However, you should not surrender to these feelings, and you should look at the good aspects of her behavior. As for any shortcomings or harshness from her, meet them with forgiveness.

As for the shabka (engagement gift): If it was part of the mahr (dowry) and the suitor broke off the engagement before the marriage contract, then it is his right, and it must be returned to him. However, if you are entitled to it, such as if he divorced you after the contract and it was half of the mahr, or if the suitor willingly gifted it to you, then it is your right. Your mother has no right to it unless she is in need and without your consent.