is it possible that she might struggle with depression or something else that might create an inability to feel a connection or be able to feel/express love, etc.?

sometimes, there are other causes of that which isn't necessarily narcissism.

i struggled for many years to feel any connection with anyone. it kind of made that cycle worse because then i felt bad that i couldn't feel anything and tried hard to make myself but wasn't able to. i guess maybe it also would depend on if your mother feels bad that she cannot feel more towards you, guilt about it, etc. or like you said, because her mother maybe wasn't loving towards her, she herself wasn't able to have that bond with her mother so those types of feelings are just something that never 'grew' in her or something.

my dad was actually like that where his dad was very critical towards him growing up (sometimes mean, i think too). so, my dad was not able to be caring towards us for many years because he kind of just reenacted what he went through and how he thought it should be. he also never wanted children even though he did pay child support for us and see us a few times a year when my parents divorced.

it took him until eight years ago today actually (when i wrote him a letter when i was in treatment for an eating disorder telling him what i needed from him and what his actions/behaviors did to me, how they made me feel, etc. i never thought he could change out of his angry, emotionally distant self, but he surprised me and has been more open, loving, and involved in my life in ways he wasn't able to be for so long.