... yes she is Toxic.
You laid it out and told her.
Which is good, otherwise people like that will continue to use you as a door-mat and as a dumpster. Causing you harm, mentally/emotionally.
I have a relative like that.
I also, detached myself/my family, from her.
Now, the 2nd issue here is:
IS this Aunt's health really what she says? Or is she just wanting attention?
Next, is she dying???
If so, then her reactions to others and her emotionality and regression in emotions... and toxicity... may be a result of, her life being so.... fragile and her life... maybe in a tenuous situation, medically.
When people are dying... they react as: sentimental and loving, or they lash out. Because, it is a process of grieving and regret or life or embracing their life they had.
My Dad, died after a long illness. People in bad health ebb and flow in their emotions... and their reactions to it. And in reaction to others... being bitter or not, or graceful about it or not.
Again, I do not know, the extent of your Aunt's health or prognosis.
But, IF the case is, that her illness is degrading her life, then she may be reacting, in light of that.
And lashed out on you. Displacing her inability to handle her most recent health scare.
Melanoma, is the most deadly of skin cancers.
But as you said, this Aunt has never been a kind person.
But the whole scenario of what she is dealing with, her health, may very well have colored... her recent tirades. And as you said, she trashed your parents too in a very hateful manner.
Yes, this Aunt, is toxic and mean.
And you live with that legacy.
But, most probably, this Aunt does not know how to handle things in a normal manner.
AND is she alone? Has a Spouse? Or is just by herself and has no friends to get support from, per her recent health prognosis?
But yes, you have a right to designate your boundaries.
She is, very Toxic.