I have it and it works I was one of the first people to get it I have had it for more than 20 years now

Peanuts is right. They will make the incision across the neck this is to put the wires or leads in. That's where they connect to the vagus nerve. The implant device is usually in the area bellow the collar bone. The incision is usually near the armpit. Its usually about 2 to 3 inches long.
I just had mine replaced last month. So this might give you a general idea of what the scar will look like near her collarbone. The one on her neck, once it heals, hardly shows. It shouldn't need to be opened again unless there's problems with the leads and the need to replace them. Which is rare.
The vns runs on lithium batteries like your cellphone.
There's a picture of my scar now. Mine was replaced April 9th. But you can see they heal fairly quickly.

No the VNS means: vagus nerve stimulator. The vagus nerve exists in a person’s neck on the left side. The stimulator is inserted in the left side of a person’s chest, over their rib cage. Two lead wires from the stimulator reach the vagus nerve in a persons neck, When a person has a seizure a magnet 🧲 is placed on top of the stimulator it sends a signal to the wires, and a person feels a little pinch where the lead wires are attached to the nerve. The strength of that pinch can be changed. Look on the Epilepsy website to learn more about it.

I had my battery 🔋 replaced and it works perfectly.

I had my VNS 2001, replaced battery 4 times. It works fine!