As soon as I read this, I saw this exchange in energetic terms - that "friend" got rid of their poisonous secret, like in a confession, and passed it on to Mary.
Quite literally, like taking a ball of energetic poison and shoving it into Mary's energy body - where it's stuck, and making her feel sick.
This sort of thing is really nasty on many different levels, and it's dangerous.
Mary is right to be worried. This can make you physically ill, and the nightmares are telling us that it can make you mentally ill as well, if nothing is done about it.
Luckily, I also saw the answer to this.
It's easy when you know energy magic.
Here's what I said to Mary:
"This poisonous secret is actually not something imagined, it's energetically perfectly real.
"You need to get rid of it - make a confession to pass it on.
"But not to another person.
"Go outside, find a stone, find a private place and tell the stone *everything.*
"Let it all come out and keep going until you feel it's all gone and there is nothing left of that stuff.
"Breathe deeply and sit with the stone for a while to make sure it is really all gone.
"When it is, take the stone and put it somewhere in nature - throw it into a river, a lake, into the sea, into a field, a grass verge or even into the gutter, if you're in a city.
"The sun and rain, moon and stars will eventually wash it all away and then it will be gone forever."
Is there a "poisonous secret" that you carry around and that "bears heavy upon your soul"?
Do this spell and feel better.
And remember - this is only energy. Energy will flow and move if we give it permission to do so, because that is its nature.
Sending blessings to all,
PS: If you feel in need of psychic protection as well, this page has lots of good ways to do this: