I'm going to ask my girlfriend not to share what I consider to be personal information
What would happen if she shared this info?
Well, I know that sharing personal information is very bad for business.
I get where you are coming from and she should not reveal your personal information. Some information is meant to be private and it's best to keep things secret from a business perspective. Otherwise, it could affect your negotiation tactics and you might even lose your "trump" card.
So what can I do if she does it again?
Obviously, she might have a hard time keeping things secret, so I suggest going forward, you should stop telling her things that can affect your business and put you in a difficult situation. Worst come to worst, you might have to decide which is more important to you. Your business or her.