I'm curious as to how exactly does the answer to your question relate to your decision. What's the motivation to find the answer? Are you hoping that if it's a choice that in the future she will choose diferently or is the sudden news easier to swallow if it is written in her dna?
I feel for you. All matters should be put out on the table BEFORE a decision to move in together in the same town let alone 800 miles away. Have you asked her why she's dropping the bomb so late?