She can be as brazen as she wants. She agreed, in writing.
As for those who say to just avoid troubles with her, she's the one causing them. She gave her approval and you trusted her. You've continued on and she wants you to take down published chapters that have already become past-tense as you have more published after that.
Legally, she has no grounds. Morally, she has no grounds. You don't owe her anything.
I'm not trying to sound uncaring or harsh, but she's behaving like a spoiled brat. You say you're worried because she's brazen. No, that's spoiled. Sounds like she's gotten away with this before because she knows people are afraid since the character is hers.
You took legal measures by giving her full credit and full disclosure in your work that this was her character. You're obligations have been fulfilled.
Don't take down your work. You worked hard for it.
You know, I'm going to get maybe a bit out on a limb here, but now that I'm typing this and thinking about it, it's really ODD that she did this. What excuse did she give you? How well do you know her? Do you think it's possible she did this to you on purpose?
At any rate, LEGALLY SPEAKING, she has no right to tell you to remove anything. Everything is in writing, you gave full credit, she waited until after it was published to notify you of an issue. Nope, you're the one in the right. If she tries taking this to a lawyer, they'll douse her claim like the dumpster fire that it is. I keep saying it but "in writing" is a magical charm lawyers won't touch.