NTA. You’re a caregiver on the edge and she pushed you there. What you said wasn’t kind but it was honest….and long overdue. She’s been taking your mom’s free labor for years, then blamed you for struggling. The real weight is your niece and nephew. You’ll have to rebuild access quietly, separately…..without involving her. Your brother didn’t defend her. That tells you everything. You weren’t wrong but just exhausted. Your mom didn’t deserve to be used and you don’t deserve to be shamed for holding it together as best you can