In Cantonese, a woman would call her mother in law her "家婆" or her "奶奶", and address her only as "奶奶".
My understanding of the same terms in Mandarin is, a woman would call her mother in law her "婆婆" and address her as "婆婆" as well (Cantonese do not do that, because "婆婆" can mean 外婆 - 'mother's mother ' in Cantonese)
My question is, do Mandarin speakers use the term "家婆" to refer to a woman's mother in law?
I also suspect Mandarin speaking women do not address their mother in law as "奶奶" because "奶奶" could also mean grand mother (father's mother) in Mandarin. (Cantonese do not use "奶奶" for "father's mother", Father's mother is 嫲嫲 or 阿嫲 in Cantonese)
Note: when Cantonese people mention Mandarin, we are referring 普通話, the official standard Mandarin dialect. Sub- dialects within Mandarin are not considered.