Sounds like another case of not protecting content before the cows are out of the barn and now trying to herd it all back in, which is way worse than if you protected it to start.
Based on a couple of comments posted her i think some people are confused, these are not comments posted on her site, these are comments posted on OTHER sites.
If I understand the proper properly, they've scraped her content and spammed it elsewhere to POSSIBLY damage her rankings, but I think it's more likely they're trying to use your content to simply get some of your traffic without doing any of the work. Not negative SEO the way you're thinking about it as it normally would rank below you site if Google has correctly identified the author, but it still steals readers and has the potential as others have mentioned to render your content duplicate content and useless if they spam it all other the place as Google might mistake it for being from an article farm or worse.
The solution to your problems are:
1. Start Bot blocking ASAP to stop the proliferation of your content from appearing all over the web. There are some good scripts out there that just plug right in, get one yesterday.
2. Set your pages to NOARCHIVE and block the internet archive from copying your site to eliminate alternative sources of your content. See [
noarchive.net...] for an enlightening read.
3. Start filing DMCA complaints with Google and the host of those sites hosting your comments, get them knocked offline
4. If they actually link to your site, go into Google's WMT's and disavow them all. If you have a budget, find and SEO company with power house disavow tools or a disavow service to wipe them out for you.
If you really want to stop it for good it's WAY more complicated than this, I've gone over the topic many times as have others, esp. in the spider forum here on WebmasterWorld, lots of reading.
I think the list of sites the spam is being hosted on my be interesting to know, esp. if they're an actual ring of garbage sites being used just for negative SEO comments.
Perhaps try writing to a few of these sites and ask them why they aren't using such tools like Askimet to stop the spam from showing on their sites. Perhaps they aren't aware of it, or perhaps the site is abandoned or neglected and they aren't aware of the problem which is often the case. Sending a few emails and waiting for some replies for a week might answer that question.
Check the IP of the sites hosting the comment spam and see if there's anything in common, if yoy find clusters of sites on the same IP then you know it's possibly done on purpose or even worse, someone set up a network of sites now abandoned. Either way, I'd try to DMCA them out of Google and off the host, send to both.
Been preaching the bot blocking content control message for years now and everyone ignores me, it's not a big deal, no need, until it hits the fan, which it always does eventually, and suddenly I'm their best friend as well as someone else with powerful disavow tools to clean up the mess ;)
Good luck with fixing this!