Reading the sources, it primarily sounds like she was embarrassed of looking like an old lady in the photo, and afraid of Nazis striking back at her and her family.
One of the sources is her husband's coworker who said, "Danuta was mentally ill, but she had a solid hatred of Nazis as a Pole. She probably got caught up in the hateful atmosphere that was whipped up against the NRP-demonstrators in Växjö."
I don't care for how that's phrased, both in that he's speculating about her and that he seems to think you need some kind of personal grudge in order to oppose fascism.
If there's a source saying she regretted the action in itself, I missed it.
e: I was mistaken about that quote. It's from the article, but it's not attributed as a direct quote from the coworker. Swedish doesn't always use quotation marks, so I read it as a direct quote mistakenly, but it lacks a dash at the start of the paragraph. Without knowing the original I can't be sure how much the author is paraphrasing or speculating.