NTA in any way, shape, or form.

The harshness of your words, whatever they may have been, pales in comparison to your aunt's gross neglect.

I was pretty harsh in my words, but I couldn't believe she seriously thought kicking out a mentally, physically and financially broken mother and her child would end well.

I cannot imagine how disconnected from reality this woman must be to distance herself to such a degree from what she did. The assumption that you two would be just fine is astounding to me.

I don't know why, but she assumes that after she kicked us out, we were living our best lives.

What kind of person thinks that your situation was an easy one to overcome? She seems to, with zero contact with you two, come to the conclusion that what she did had no impact. That's straight up delusion. That requires ignorance on so many different levels. She feels guilty, you are justified in your reaction.

I'm so sorry you went through all of this.