I've done this on several occasions. The sanity loss is entirely dependent on how much they see of those from beyond the limits of human conception, as well as their own self-control. It is why many of my servants always seem so determined, because it takes a great will to salvage even a shard of functionality after looking upon me in my true form.
If she is anything like me, she would not like it very much if you are interfered with. Though if you would like to ask her, I suppose it could do no real harm.