Best way to recover from poor quality link building

[sinicline]

I have a client who has been bad affected by two UK SEO companies who built a lot of low quality article and directory links for her business. We've rebuilt her website and have been adding quality, original content every week for the past couple of months. However, her ranks continue to drop because of all the existing duplicated article and other low quality backlinks. There are around 100 crappy sites that are linking to her and removing them all looks almost impossible as there's just no motivation for the people in control of these sites to do anything.

What would you do? I'm tempted to shift the site to another domain name and put a placeholder page on the original domain. I can't ditch it altogether as it's also her company name. I'm assuming the only way to overcome bad links like these is to build some better ones but is it worth the effort required? There's been no manual penalties btw.