When someone shares a private conversation between you and another person without your consent, it is a clear violation of trust and respect. It shows that the person does not value your privacy or feelings, and is willing to disregard your boundaries for their own benefit. This can be especially hurtful if the information shared is sensitive or personal in nature.
While freedom of speech is an important right, it does not mean that people can simply say whatever they want without regard for the consequences. In this case, the person's actions have caused you emotional distress and violated your privacy rights. While she cannot legally be prevented from sharing what she learned, she still made the decision to ignore your wishes and invade your privacy. She should have either gained your permission before sharing it, or not made it public to begin with.
It is important to address this issue with the person involved and assert your boundaries. Make it clear that you do not consent to your private conversations being shared, and that it is important to respect your privacy. You can also choose to distance yourself from the person if their actions continue to cause you distress.