Most magicians and occultists generally speaking already know that the astral planes overlap each other. But the details can be quite tricky, and I will do just that- go into detail on the subject matter.
Simplistically put, referring to the Kabbalah- all the aspects of creation within this context at least are planes of existence; it starts all the way at the top, and ends up all the way at the bottom and the material world is the bottom. We as human beings vibrate on, what is practical/necessary to be brought up within the context of the topic at hand, two planes of existence – the astral and the material (The highest one like I mentioned is for the sake of discussion impractical to bring up, regardless of its supreme importance, so to speak). So bluntly put, people have an astral and physical body. The former obviously trumps the latter. All the aforementioned planes of existence overlapping each other, interwoven like an existential tapestry. And all of them end up in the material plane energy-wise, like (hypothetically speaking) the ball in the game known as pinball.
What you need to understand that, as a resident of the material plane, the astral planes overlap the material plane, similar to the example shown below. Therefore, the residents of that astral plane or those astral planes can see what you and the rest are doing in the material plane, more or less- like a bird’s eye view of the material plane. The more someone is in good standing with the astral plane, the better their quality of life will be based on the aforementioned mechanics. Being in good standing with the astral plane equals mental health in this regard. So mentally healthy people will have an optimal life free from negativity in general, regardless of their surrounding environment- they get the “long end of the stick”.

So yes, your dead grandma is seeing you have sex and more than a few of the secret thoughts you have as well as the things that you do in private etc.
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