Regret telling my friend something?

[Libby]

I'm in year 9 and I'm taking my Italian GCSE this year (early) and the examination officer guy came into the class wanting to give me something, then everyone was asking me what it was. I didn't intend on telling a lot of people just a few close friends but I wasn't looking forward to telling one of my "friends" who gets jealous easily, but she DM'd me on twitter asking what he wanted, I told her and she kept asking questions with loads of "?" and when I finally told her she didn't reply, when before she was replying within seconds.
Ugh I regret telling her so much, the GCSE is like 5 months away and I have to deal with her fucking jealousy. What do I do? Oh & there's this girl in our group who I don't like due to trust issues but we're sort of neutral, she wants to find out, I definitely don't want her knowing, but what would I do if the jealous friend tells her? I don't want this whole situation to go public because as stupid as this sounds I believe in jinxes :/ Help?