Depending, unless OP actually has notes or files showing the build of the idea it isn't going to be taken well. She can't just out right accuse her publicly she has to have some sort of proof that she had come out with it first. Otherwise, it's her word against her friends.

#43, generally they are very surprised that their victim speaks up. "Wow, Janine. That sounds just like the plan I described to you on Thursday. Don't forget to tell him about the end of it, where" and then include the extra information that she hasn't gotten to yet. On occasion, you'll get other workers coming up to you with their own horror stories about her, and then the boss gets his or her eyes opened. If not, she's now under suspicion as an idea-thief, and will have to watch her step. Don't throw a huge shit-fit but definitely stand up for yourself.

I agree with you completely that's a great idea. Though most when it comes to confront someone their idea is a rage fueled rant. Though it depends whether on the other person whether or not they'd be able to bullshit their way out of it. That's why I'm hoping OP has files saved to her comp and can show when they were created and show how it progressed. OP may not have any of those things and maybe not prepared to prove that it was her idea with anything tangible.