Not a physicist, but have had a lot of wiccan/neopagan friends over the years.

A portal to where? If you assume it does go somewhere, and isn’t just a visual disturbance of some kind, what you would have is a massive amount of energy being focused to connect two points.

I’m old and dgaf, but you can go look up the kind of math used when people start talking about wormholes. I’ve seen the kind of numbers involved in the energy required. There’s a really big value for n where 10^n is used to express it. We ain’t even talking triple digits if my memory isn’t worse than I think it is.

So, if your friend was present for a portal to or from somewhere other than this earth, I would imagine they’d be dead. Poking a hole like that is not going to be free of secondary phenomenon like black holes have emissions.

So, I would seriously doubt that what she experienced was a portal, doorway, hole, or anything like that. It has its own validity as an experience for her, but that validity doesn’t extend beyond her.

If you want the woowoo spiritual explanation, it would have been a symbolic representation of a doorway rather than a doorway itself. You can easily learn to visualize so strongly as to have the imagery seem very close to reality. There’s weird folks out in the world that don’t even have to try; they just have highly visual imaginations, and it takes very little for it to become very realistic. Don’t even ask about my dreams in that regard, or how easy it is to have what amounts to hallucinations if I can get deep into a book.

So, someone that is spending a great deal of time focused on “spiritual planes”, or whatever, is very likely to eventually either find something they can convince themselves is spiritual and “real”, or outright placebo themselves a numinal experience. And, you can’t prove a negative, so maybe they do experience something that has an objective reality that we can’t detect. But, you know, wiccans be trippin, even when they aren’t smoking herbs.