My out there Rey theory
In the early days of the First Order, just post Return of the Jedi, Snoke knew he needed a powerful Sith apprentice to have any prayer against Luke Skywalker. To this end he instituted a program taking what was known of the Emperor's cloning procedures and tried to create a Force being from genetic material of Luke Skywalker.
They also added in memory ingrams that were supposed to kick in automatically so that the clone would be powerful right from the get go, no training needed. Problem is the experiments were all failures. None of the clone kids showed any real Force potential. So Snoke had them killed/abandoned/dumped. He moved on to another plan, which was corrupting the son of Leia/Han, Ben Solo (Kylo Ren). That plan worked.
Rey however one of those discarded clones. Dumped on a desert planet and abandoned by some parents who didn't want her. Just one thing ... latent Force abilities kicked in for her as she entered adulthood.
Snoke done fucked up, in other words and now she is the blood of Luke Skywalker and is going to bring back Balance to the Force.







