One of the most toxic friends I've ever had reached out to me and I couldn't help but take the bait
And what did this friend say to you?
She said it had been a long time since we broke up and if I was interested, I should go out with her
It was probably a good thing for you to end this toxic relationship in the first place.  If your friend is reaching out to you, she might have changed her ways, but if it sounds like she is the same person, then you shouldn't try to get involved with her again.
I think she really changed and I should take her back.
Then take a chance and take her back. Just keep an eye out for the red flags that initially tipped you off.