Honestly, I'd very flatly tell her "I've told a very small group of people, this is private information I shared with people I trust, knowing they would not share it with others. I'm asking you not to tell people, and if they ask you directly, tell them you don't know and they'll have to ask me." Give her a line in the sand (I'm not broadcasting and neither should you) and an out (this is exactly what to do if people ask you). Then drop it.
This isn't foolproof. She still might tell, and quite frankly she might already have told if she's hinting that "people will know" and she's trying to get out ahead of you hearing about it. But this at least puts all your cards on the table, avoids any question of her being jealous, and frames it entirely as it being your information, your responsibility to share, and your placing of trust in her NOT to tell.
Either way, prepare yourself that the information's already been shared and get ready to roll with it. The important thing is that you made a life decision for yourself and you're benefiting from those changes - what people opine about your decisions is about as important as how they feel about your new car or the shade you painted your front room. This impacts them... how? Not? Oh, not, it does not impact them at all, so big whoop about their opinions.