So I listened to the documentary that was sourced as the origin of the quote. I wrote a comment here.

In essence, it doesn't seem like she regretted punching a nazi per se, but that she feared that it'd cause the life she'd worked so hard to build here to fall apart. I'd imagine that I also wouldn't be very fond of seeing an image my mother hated popping up left and right, and being reminded of what she went through because of it, even if it is as a symbol for a cause I align with.