"the last woman"
This is little tricky. In English if you only had 'last', it would not be THE last. To make this poor woman to be the very last woman, it has to be preceded by THE. And THE LAST thus means 'poslední'.
Even in English if you wanted to point out THAT particular last woman, you would likely use THAT.
Ta poslední žena just sounds quite weird in Czech. Why pointing out it is TA when we know she is the last. Does it make any sence??
... a little :D. I think it would make more sense within the context of a sentence - but just as a simple article+adjective+noun thing I still feel technically there could be a "ta". But nitpicking and all that and also - not a Czech speaker (yet!). (btw, wrong time and place for this, but thank you SO MUCH for developing this duolingo course - after two years it's finally kicked my butt into getting more serious about learning Czech!)