The example that made me post the OP was, now i think about it, on Facebook, not Twitter, as it happens. A friend of mine posted on FB that he'd been to a concert by some band or other and one of his friends commented that she was "so jealous". I thought: she means she's envious.
But as atqui says, the meanings will morph and jealous will come to mean envious because that's how most people use it.
Then i start wondering how long it will take before only pedants use 'envious' when they mean envious.
Has disinterested lost the battle yet? Pretty much, I reckon. It's a shame to lose words, but i suppose we are making them up too.
Sorry about the small i. The way my iPad capitals work has changed and I haven't quite got the finger timing right yet. Fed up of correcting though.