In Bereshis (Perek 18) why would God appear to Avraham regarding Sarah’s laughter and not appear to Sarah herself? Isn’t one’s relationship with God personal, not necessarily involving one’s spouse? Please source any answers!
The Chizkuni explains that Avraham was worthy of rebuke above that of Sarah. Avraham also laughed at the notion of having children at such an old age, and his behaviour required more of a response from G-d. The Chizkuni writes:
למה זה צחקה, “why is it that she ridiculed, etc.?” [the author now repeats something he had already explained, at the top of this page, offering an alternate explanation. Ed.]“If you were to ask why G-d did not rebuke Avraham when he entertained similar doubts in Genesis 17:17, the answer is that seeing that Sarah is considered as on a lower spiritual level than her husband, it is considered as clear that if even her doubts were criticised, her husband’s doubts were deserving of a rebuke even more so, without the need for the Torah to spell this out. Our author uses a parable to demonstrate this point, writing that when a wise woman wishes to rebuke her daughter-in-law for something both she and her daughter had been guilty of, she rebukes only her daughter instead, allowing her daughter-in-law to draw the necessary conclusions about her own behaviour. If G-d had rebuked Avraham in Sarah’s presence, he would have felt ashamed; He therefore did so in an indirect manner. (Sefaria translation)
So in appearing to Avraham, Hashem was not telling Sarah off through her husband but it was first and foremost, a rebuke against Avraham.
Ibn Kaspi in his commentary there writes:
לא אמר זה לשרה כי אין לנכבד ולקדוש שידבר עם הנשים ולכן נשמרתי אני מזה כל ימי
He did not say this to Sarah, for it is not [appropriate] for one who is honored and holy to speak with women. And therefore I have guarded against this all my life.