What is the religious ruling on a mother's supplication against her son after he refused to bring sweets for the Prophet's birthday, and is this refusal considered disobedience to parents?

Celebrating the Mawlid (Prophet's Birthday) is an innovation (bid‘ah). Preparing food on such occasions is among the reprehensible innovations. Your refusal to bring Mawlid sweets is not disobedience to your mother; rather, it is a rejection of what is wrong (munkar). You should advise her gently and explain to her that your abstention from this matter is due to its contravention of Allah's command.