What would possess her to break her promise to me?

I have this girl I work with(lets call her jane) that is a friend of mine. I trusted her pretty well until tonight. I told jane a while ago how i am interested in this other girl i work with (lets call her meg) things were well for a while and then tonight another girl i work with told me she heard from a little birdie that i was interested in meg. I asked her how she knew this and she said she couldn't say who told her. when i asked her to tell me so i know who not to trust anymore she told me jane had told everyone in the store, and she was pretty sure that meg knew as well. well this made me furious, I admit instead of making this a grade school level of maturity i could have just manned up and told meg how i feel. however, she just broke up with her boyfriend or several years so i was going to give her time to recover before i made any sort of move. but now those plans are ruined because jane couldn't keep her dang mouth shut. why is it so impossible for some people to keep a private conversation to themselves? Also, does this pretty much mean my chance with meg is shot? I just feel like things are going to be awkward at work now. I know eventually i will forgive jane for this but i don't think i will trust her the same again. what is even worse is I already have a hard time trusting people so this just reinforces my feelings or mistrust in others. I understand not all people are like that but why would she do this? The thing is that the girl who told me my private conversation wasn't so private anymore waited to tell me until meg had left. I just feel so stupid and embarred, what should i do?