Oof, glad that didn't result in contact!
I had the same thing happen once- she did see me for sure, but made that right turn right in front of me anyway. If I hadn't slammed on the brakes I'd have had my person introduced to the side of a Suburban.
Her action was so egregious that I poured the coals to it and followed her- she wasn't expecting that biker to nearly put his hand through her back window and she just about hit her head on the roof when I spanked her truck. I don't think she'll be doing that again... if she does, she better make that first hit count.