Ok, back story.
I previously posted a couple of threads earlier in the year (january) regarding my colleague who is hell bent on making my life a misery. She is extremely manipulative, used underhand tactics to try to undermine my work, and has bullied me out of earshot of other members of staff. On top of this, she foisted a job she particularly hated on to me because it was a busy part of the role which meant she couldn't wander off, and she kept on with the easier jobs.
Anyway, on the Monday just gone, our manager came to our dept and said that they now only need 1 person to run the department, not 2. The part that my colleague foisted on to me was remaining, and the role my colleague was doing was being moved to another dept. There will be no job losses, only a move to another dept. She explained that all respective managers were visiting their same depts across the Trust on the Monday to advise their employees, so everyone knew at the same time what was happening. My colleague, however, does not work on Mondays.
I asked our manager if she could come and explain all this again to my colleague the day after, (tuesday) as I thought it would be better coming from them, not me, as I didn't want to get a word of it wrong, worrying how she was going to react.
Anyway, the manager came back the next day and told her, and I explained to her there and then that I thought it was up to the managers to tell her, not me. Of course she was very pleasant while the manager was there, but as soon as she left, she went quiet, and kept on leaving the dept. Not long afterwards, I went home so that was that.
I was off on weds, but when I came back on Thurs, I found her doing the job she had foisted onto me. I told her in no uncertain terms that I knew what she was doing, and she let rip, accusing me of not telling her about the changes before the management, that I was a 'dirty, sneaky conniving little b*h'. She then vented her vitriol on me, saying just the most horrible untrue things, and I just blew my top. I told her what I thought of her, that I was glad I wasn't going to be working with her any longer, 2 years of stress just came out. I couldn't stop 
I did seek advice from a couple of people about whether to tell her or not, so it was not like I was being underhand. They agreed that it should be left to management, but WWY have done in my shoes? Please be honest....