If she doesn't agree then there is no agreement and you would have to question whether you should be buying a house together at all. If you can take the mortgage solely in your name then the house can go solely in your name. She would have no claim unless she contribute to the house or to the family unit. In that case she may have a claim for a capital payment on a separation. See online section 28 of the Family Law (Scotland) Act 2006 which provides a mechanism for "compensation" after a separation which is also illustrated by the Supreme Court case of Gow v Grant which again you can read online.