DS is 26 and his girlfriend is 21. He has a large amount of money that was used to purchase a flat from when his father died. His girlfriend recently moved in and now they are buying a house together. He's putting 100k into it and it will be a joint mortgage. Doesn't that mean if they split, she will be entitled to half of that? He says he isn't concerned about that at all. But AIBU to be slightly worried here?