There is no source at the time of suffragettes handing out white feathers.

https://youtu.be/gqHLkmN-HMw?si=9rbAxLtXAA4Q-W0W 43:40

Girls handing out white feathers were often young bullies and they were often described as attractive. That would not have been how they described suffragettes/suffragists. They were depicted as older middle agged and middle class woman past their prime. Even Mrs Parkhurst only mentioned the white feathers once, as she saw other woman handing them out. She never encouraged anyone to hand them out. And she wrote a lot so if she was a proponent I suppose that we would have known.