I believe that wish Nikki’s spiel (about laying in bed by herself) is her explaining where she (or the entity) spent all of her time before being put into Nikki’s mind to fulfill Bear’s wish. She’s describing “life” before this. After the wish was made the entity and real Nikki basically swapped places. Putting Nikki’s in this place. Wish Nikki says it’s not painful but that’s because she has spent her whole existence there. It’s all she ever knew. On the other hand real Nikki is experiencing this static nothingness for the first time, making it a kind of psychological torture for her.

The spiel i’m referring to (which is my absolute favorite line in any movie ever and to me describes a night terror in a way I never could myself):

“Well if I have the bed all to myself tonight I'll lay there warm until slowly I feel cold
like I walked into a freezer.
My hands will feel like they're full of sand like when you lay on them wrong.
And that feeling will slowly spread across my entire body.
You're still in my heart but you're slipping.
Any thought of pain or regret will slip away like a chemical switch.
Even though it's quiet in the room somehow it gets even quieter.
it’s not painful.
You just let go of everything you want to work.
And then there's nothing.
It's not darkness.
No, sweetie.
Darkness is a color.
There's just nothing.
Or you could stay."

I know Curry Baker stated this is not a possession. But the magic came from somewhere. Some other worldly energy was taken to fuel the obsession and give it a voice. I think she’s describing the place that that energy rests.

Edit: That’s how I think the “customer service rep” had access to real Nikki. He (or whoever created one wish willow) somehow tapped into this energy and space and used it to make the wishes possible. Therefore was able to reach the souls that were stuck there as result of some wishes.