What is the ruling on students of a Quran memorization class giving a gift to their teacher's mother after completing the Quran and the end of the semester, while the relationship with the teacher continues for review?

There is no harm in giving gifts on joyous occasions, such as the completion of the Quran, rather it is commendable, based on the Prophet's (peace be upon him) saying: "Exchange gifts, and you will love each other." As for the gift that is forbidden in Islamic law, it is that which is given in exchange for a right that must be fulfilled or a wrongful act that must be abandoned; this is a bribe, and its perpetrator is cursed. If the gift does not influence its recipient to give to the undeserving or withhold from the deserving, then there is no harm in it.