That is such a shame. Your mother is supposed to be someone that you can confide in, not someone who blabs your private business to all and sundry. The least she could've done when you confronted her about it was apologise, say she didn't realise it was confidential and promise to keep her big mouth shut in future. Instead she chose to blame you for her bad judgement!
I think you're wise to stop telling her anything you don't want made public!