I don’t think she said she was a Democrat. She said “I’m not a Democrat”.
She is a Democrat.
She happens to support the President.
I heard “I am a Democrat,” and wondered about that. She surely doesn’t sound like a Democrat. But then, I am a registered Democrat, too-have been for almost forty years since the time my wife and I decided it was time to become Citizens and register to vote. We flipped a coin to see which of us would become Republican and which Democrat.