It’s a pretty brilliant lyric.
The archetype of the witch represents women in power.
In history, if a women was powerful, they called her a witch, because the only way to explain her power was that it was due to some otherworldly power.
But the true greatness of the witch archetype is that it’s about a powerful women getting power only from herself, not from a man or a job or a position: the power comes solely from within her.
In regards to the burning, society would burn witches after judging and condemning them for being strong or sexual or powerful, or whatever it was that caused them to fear them. They feared them because they were out of place, out of station, out of their lowly position.
To quote from Half Hanged Mary, a Margaret Atwood poem about her ancestor who was hung for being a witch but survived:
“Before, I was not a witch. But now I am one.”
She wasn’t an outspoken, powerful woman before, but after society’s condemnation, she became one.
In this specific song, Taylor is referencing how society would call a women a witch for doing something she wasn’t supposed to. She was too powerful. She was too sexy. She was too smart.
Or in Taylor’s case, they condemned her for something she wasn’t.
With this lyric, Taylor is saying, yeah, I’m a powerful female, so if you wanna burn me, burn me.