My parents are both gone now, but I have several people in my family that are as you describe. I have learned over the years to not tell them ANYTHING. When I find out someone passes information along without my permission, they get cut out of the information stream.

It's a hard lesson to learn and it makes it hard to have an actual conversation with any of those people, but I value my privacy and I cannot stand when someone makes my information theirs. When they ask nosy questions I just look at them in absolute silence or put them on the spot and ask a question like "why on earth would you need to know that?" or "why do you ask?", or just change the subject. If they continue to bug me I tell them right straight out that I don't care to discuss it with them and why. Most people stop bugging me after one run through the mill. It's not my problem if they are insulted because they have diarrrhea of the mouth.

I am sorry that you don't have the relationship you want with your Mom. Sometimes we have to re-define our relationships to what we can live with, even if it is not what we need or want from that person.