I asked a similar question here some weeks ago. In my case, there's no divorce but for financial reasons I am likely to have to sell my house and move in with a girlfriend who rents a place. Anyway the answer I got - and I would think this applies to your friend too - was that capital gains tax would only have to be paid if the house she was selling was NOT the main residence. In other words, if that was her home, then whatver she makes on the sale is hers, if it was a second home and not her main residence, then she would be liable for CGT.