Personally I’d stop long psychological conversations with her on the phone as it seems to always result in fights and drama.

Maybe your sister keep phone conversations to a minimum not because she is shallow (?) but because she doesn’t want to be sucked in toxic drama. Or maybe she simply doesn’t have the time for this. Most busy people don’t even have the time for long phone conversations.

My dad is quite toxic and if I engaged in these long conversations with him discussing other relatives or some other drama, we’d fight all the time. I avoid that. You don’t have to neglect your elderly mother of course. Do go visit, brung her things, help her out but you don’t need to get sucked into drama every time.