From the Forbes.com article on the story:
Rose admitted that it was unusual to use the company Twitter feed to express her views, but, she wrote, “when the company you dearly love is being ruined,” she felt it was justified. “There are over 60 of us being fired at once!” she wrote. “Mass execution, of loyal employees who love the brand.”
One of the most entertaining tweets that came through before HMV took back the account and deleted the offending tweets: “Just overheard our marketing director (he’s staying, folks) ask ‘How do I shut down Twitter?’”
After she stopped tweeting on the HMV feed, Rose continued to tweet on her own account, @poppy_powers, using a hashtag she created while tweeting on the HMV account, #hmvXFactorFiring. She explained that she had worked as an intern at HMV and in that job, had been responsible for the company’s Twitter and Facebook accounts. Because she is single and has no kids or mortgage, she wrote that she felt she was in a unique position to speak out.
Since Rose was already slated for termination, obviously she may only need to worry about the employer pursuing her for whatever claim fits this incident in the U.K., not to mention any damage to her reputation in applying for future jobs.