Suburbia

I’m trying to figure out if my wife needs to pay any capital gains on selling her share of a property she jointly owns with her brother. The property was bought for £212k on a joint ownership mortgage. Her brother is now remortgaging so that my wife will be off the mortgage. The payout from this will be £50k. She hasn’t lived in the property since mid-2020 and this is not her main home. Am I right in assuming that as the payout is less than what her share is worth, there is no capital gains on it?