I guess it all depends on your original reasons for buying in the first place. If it was bought for investment, then you could be waiting a very long time to realise any return in terms of capital. I have watched the prices on LT for over two years, and the price of apartments has not moved. Lots of people are placing adds saying “for sale at original contract price”. PW don’t help by selling off plan apartments on new developments cheaper than LT prices.
If you need to rent out to cover mortgage costs, then once again in my view you may struggle. There are about 1,800 properties on LT, many identical apartments, lots of competition.
I also think your friend may well struggle to sell half a property.
It may be worth both of you selling up and sharing the loss after all costs are taken into account.
However, if it was bought for holiday/own use etc., then I guess you need to decide if you will make full use of it yourself