First password protect your cell phone and laptops or any other device you have that she might be able to pick up,and if she does pick something up tell her to please put it down as it does not belong to her.

Sure she will get upset , but YOUR upset that your privacy is being invaded and rightfully so.

You should have a talk with her and explain that you are going to live your life and sure you will agree to hear out her opinion but in the end you are going to make your own decisions what your going to do and who is in your life.

I had to do this with my Mom years ago, wasn't easy but I felt so much better once it took place and I told her that she can certainly have an opinion but if she kept going on and on and not respect me that I would just get up and leave, and I had to do that about 10 times give or take, I remember driving away and bursting into tears , But I made my boundaries clear and stuck to them.

Sure she will be upset, But its your life and she will most likely get over it. If she starts to get on her Gently remind her of your stand on this , if she insists just leave... Don't back down. Months down the road things settled and we actually had a much better relationship due to my placement of healthy boundaries.