Communication is key here, anonymous. It’s important to set boundaries with your musharna and make it clear that although you appreciate your help, you don’t feel comfortable with her sharing your most intimate thoughts with another person. It may help to visualize with the utmost clarity what you think would happen if your best friend were to see these visions so she can see your viewpoint in terms she understands.
Additionally, consider confiding in your musharna more often. She may be attempting to make herself “useful” by connecting you to your best friend, but if you give her another purpose, such as talking to her about your feelings whenever you can, she may feel less inclined to act on her own in order to make you happy.
Best of luck, anonymous!