Yeah, I wasn't super impressed by the timing, and I have questioned her about the house. She says they cant afford the mortgage separately, cant afford to buy each other out, and it would be too weird to live as flat mates, so I am pretty sure it wasn't done with an intent to get a nice house. Just younger people not thinking about consequences.
I am mostly sure shes not in another relationship. She knows about my history (one of the VERY few pepole here that does) and as she is still angry with her dad having an affair, I think that's not the issue. More a WAW sort of situation