Thanks for all your replies. I'm now more confident on how to handle this. As my mother observed, you're like me in these situations, except you walk away sooner!

Rather than not like her, I dislike how she's been using me. I admire her for getting out of an abusive relationship but don't like the attitude when something doesn't suit her. Latest problem is ex wants to take son on holiday, so she needs to give permission. Despite my attempts to explain why airline needs permission letter from her, she couldn't get past the need to do it fearing ex will use her passport details against her. After being told (again!) that I didn't understand, I suggested contacting airline, travel agent or consulate/embassy to find out how to do this. Although I know a lot about travel, this isn't an area of expertise.