My MIL also loved to complain about "favoritism" of the mothers of her kids' spouses, including throwing a fit about the one who was providing unlimited free babysitting when nibling triplets were toddlers (BIL and SIL were like, She offered. Did you want to offer free babysitting? Be our guest, and she actually did start to babysit for them occasionally) and crying because my wife and I asked my mom, who has been fixing up houses her whole life and even done paid work for a contractor friend of hers in the summer, for advice about woodworking and painting and tiling instead of her "even though she was right there" (she had no relevant experience).

Anyway, my MIL had an inferiority complex due to childhood abuse. I suspect there might be something going on with LW that is more appropriately dealt with between her and a therapist than between her and her daughter.