Adult child struggles to trust mom with private matters

DEAR HARRIETTE: I love my mom, but I just can’t trust her with any sensitive information. Every time I share something personal or private, she turns around and tells my family, her friends and even acquaintances, and it’s incredibly frustrating. For example, I’ll confide in her about something going on in my life, and the next time I see a relative or one of her friends, they’ll start asking me about it. It’s awkward and upsetting because it’s often information I never wanted these people to know. It’s gotten to the point where I’ve had to become selective about what I share with my mother. I hate feeling like I have to filter everything I say or keep her at a distance just to maintain my privacy. I’m 29 years old, and I feel like I should be able to have a trusting relationship with my mom where I can share things without worrying that she’ll broadcast it to everyone. I don’t know how to get her to stop doing this without hurting her feelings or creating a bigger issue between us. I don’t want to completely shut her out, but I also need to protect my personal boundaries. How do I address this with her in a way that will get her to understand why I’m upset?