Am I being mental?

I’m around 10 weeks pregnant and mine and my partners parents know but we asked them not to tell anyone cos it’s early days and anything can happen. Last night I found out that my partners mum told all her friends in the pub our news when she was drunk! I am very angry by this as she has betrayed my trust and told people I barely know my private business, but my partner doesn’t think his mum has done anything wrong.. where would you stand?