Seeking advice with dissertation chair: possible theft of idea and possible blackmail
In my view, you did well. It is very courageous what you have done so far and science needs people like you.
The difference with the girl you refer to from two years ago is that probably she had not contacted the ombudsperson and you are second. I suspect there are more cases. Would be good for you if you discretely can find out as it may help your case.
It is difficult to predict the outcome in these situations but I believe on a higher level in life, you will succeed whether here or somewhere else. Shallow comfort: Your case will also add to the file of this supervisor.
You did not ask for this to happen but it did. It is not your fault. It may take you extra time but in the end it will enforce your personal strength.
You may consider to ask the ombudsperson to start an independent investigation. An ombudsperson can start such investigation if there is sufficient reason. In that case he/she should able to keep you out of shot and a formal complaint from you should not be necessary.
Take care, trust your instincts and do not let this unfortunate situation break down your self confidence.