Audreyu

That's definitely what that is! It's usually right when you're about to slip all the way into sleep. Mine always sound like extremely loud electrical zaps. It's extremely disorienting and if you don't know what it is it can cause a lot of anxiety. I've been getting them since I was around 12, when I started puberty. Tell her what it is but make sure you assure her that it does not physically damage you in any way!

This is from sleepassociation.org "Exploding head syndrome is thought to be highly connected with stress and extreme fatigue in most individuals. What actually causes the sensation in individuals is still unknown, though speculation of possible sources includes minor seizures affecting the temporal lobe, or sudden shifts in middle ear components."

No side effects besides anxiety about the noise. It causes no physical damage.