Did she say she was mislead?
Natalie:
"The podcast is titled "The Witch Trials of J.K. Rowling," an obviously tendentious framing that presents JKR as the victim of an irrational hate mob(...)"
"I don't want my involvement to lend any legitimacy to this. I regret my participation and would not have participated had I fully understood the nature of the project. I feel that I have been used, and I share the sentiments of other trans people who are speaking out against it."
Has she posted any correspondence to that effect?
You want her to post chat logs and email correspondences on Twitter to prove her case? That seems a tad bit juvenile. Some of the agreements could have been verbal too. You may argue that it was foolish of her to not sign some kind of elaborate contract before going on the podcast, but that doesn't mean that Natalie is in the wrong morally speaking.
Ultimately you have 3 choices here:
A) Believe Natalie
B) Believe that Natalie is lying about being mislead and simply regrets her decision
C) Believe that Natalie is lying about being mislead and was simply too stupid to see the obvious "trap"
Based on what I know about her I find B and C unlikely. She seems like a genuinely good person and she's definitely not dumb.
None of us have proof, though. You can go for B or C and be no more wrong or right than me.