Joint mortgage and separation - Scotland

My friends wife moved out of the family home in March for some “space”. In June he received a letter from his wife’s solicitor stating that the marriage had irretrievably broken down and she was instigating an amicable separation. This was a bolt from the blue and he was devastated. His wife has since moved into a rented flat but she is still paying half of their joint mortgage. My friend is paying the other half of the mortgage and all other associated costs of the marital home. His wife is now pushing to get out of her half of the joint mortgage. Can she do this? My friend is still suffering from the shock of the situation and doesn’t want to rush into anything at the present time (he still hopes that they can reconcile) but surely he can’t be forced to sell the house or assume full responsibility for the entire mortgage already? Please advise