Whingeing sister
I didn't get the character of the sister at all. Been in USA 15 years, all but her eldest child must have been born there, but still feels homesick. And yet it seems she has never been back to visit mum and family in all that time? And speaks far better English than you would expect?
I reckon once people get a good life established as migrants (and I know because I am one myself) they settle down within well under 5 years and reckon it has been a great move. Just look - her husband is a doctor, they have a very nice house, big car, the lot. Prior to this current downturn in his business they are very successful migrants indeed, when what they could have had in Palestine was ... well we saw it!
I found her a grating annoyance in an otherwise good film, and really pitied her long-suffering husband.