Lots of possible reasons for that. Maybe actually leaving scares her so she lashes out at you to deal with the fear. Maybe leaving on friendly terms makes her feel more guilty, so she gets angry with you because then she can justify her decision to leave to herself. Or maybe your changes and detaching makes her angry because she feels she is losing control. Maybe a combination of some or all of them.
Point is that you just need to be the emotionally detached rock. Let her be angry, you be calm. Let her be vitriolic, you respond kindly. Let her be passive-aggressive, you be forthright and non threatening. Let her be accusatory, you be mysterious.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018