She is not back.
That Twitter account is obviously a fake. Someone has made a fake account pretending to be her before, it's probably the same guy.
How do I know it's fake? There are no personal pictures that could have only been taken by her (well there is one that could have been, but that could have been found elsewhere. I expect more than one), the grammar is incredibly bad (broken sentences with words missing, misspellings etc) and the fact that it was tweeted "#Now I'm available for chat, only here. So don't miss the chance to interact. #SaraStone" why could she chat "only here" if she's the real deal? Seems suspicious. She has also retweeted every message talking about here which I find odd considering the few interviews I've seen of her she seemed pretty self centered (nothing wrong with that though). Her personal website doesn't link to the twitter either. It's more likely that this is some pervert getting off at pretending to be her.
Unless we can find more definitive proof it's her we should assume it's fake.