There is no doubt that the working actress was a real blog. The associated twitter account still exists, and was active between 2010 and 2012, with links to theworkingactress.com. It's not possible to backdate posts on twitter, which means that, during that date range, there was content at theworkingactress.com. Unfortunately, not only has the blog been taken down, it's been excluded from the Wayback Machine.
Additionally, at least four people interviewed the woman behind the blog between 2010 and 2012 via email. Those interviews have tidbits that could point to Meghan (and some that don't), but whoever she was, theworkingactress was really good at answering questions without giving away too much information.
Without being able to read the actual blog posts, I wouldn't be willing to make a judgement call either way about whether or not it was Meghan.