In a word - no...
If the mortgage payments are not met, then the
mortgage provider can chase both parties for payment.
As he is in the
house and she isn't she could ask him for occupational rent for enjoying
her half of the house.
Although, depending on
court/judge/stubborness etc, your partner could claim that the money paid
by him in the last two years should come back to him and she should not get
a share of that, but the rest of the money should be split 50/50.
However, I know the law is slightly different for
cohabiting couples rather
than married couples, so hopefully one of the legal bods will come along
soon and give you more details.
Best of luck
K