Sometimes it is difficult for me to tell if a letter is legitimate or if a group of young people at a sleepover have decided it would be fun to see how I’ll answer. I’ll therefore go at this from both directions:
If this is a legit question: What you report is consistent with a delusional disorder. A delusion is a conviction that something false is for real. A delusion may be non-bizarre, meaning that though unlikely, it’s possible — like the belief that someone is following you when there is no evidence to support it. A bizarre delusion is one that is completely untrue and impossible – like the belief you’re from another planet. Sometimes the cause is a vitamin deficiency or some other medical condition. For that reason, it’s important that a person with delusions always be checked out medically before beginning therapy. Delusional disorder is very rare and usually occurs during middle age, not as a teen.
If you’re joking: Since delusional disorder is so rare in teens, I again have to wonder if you and a friend decided to joke with us. If so, I’d have to say that your mother is sadly misinformed about the landing of a ship from Pluto and the exchange of her daughter for a Plutonian. Not to worry. Someone is going to take her place, too. Soon Plutonians will conquer the world.
I wish you well.