Is doubting that the utensils are plated with real gold—despite the mother stating that it is not real gold—considered an act of undutifulness and a form of ill-conjecture towards her?

The doubt you experienced regarding the truthfulness of your mother's words is not considered disobedience or ill-suspicion; rather, it is a self-thought for which there is no accountability. We caution you against obsessive whispering (waswasa). As long as your mother has informed you that the utensils are not plated with gold, and you possess no evidence to the contrary, there is no harm in using them, and there is no need to seek out the truth, as this might be waswasa. It is worth noting that some scholars have permitted the use of vessels plated with gold or silver.