Is the money borrowed by the mother from her brother, under the pretext of her son’s educational expenses, but which she spends on household needs, considered deception and thus Haram, given that the father is alive and experiencing financial hardship, and the maternal uncle does not demand repayment of the loan?

If your maternal uncle gives your mother money as an act of kinship ties (silah), piety (birr), and benevolence (ihsan) without requesting repayment, then there is no harm in utilizing this money for household expenses, studies, or other needs. The matter is broad, and such a gift is considered an act of transferring ownership of the money.

As for your mother mentioning your studies, it is likely to alleviate embarrassment rather than to deceive, as she is asking out of need and not for saving. Therefore, it is advisable to avoid excessive scrutiny and baseless suspicions, to have a good opinion of your mother, and to show her dutifulness (birr).