The thing is that most Asian girls see the job as a FA a stepping stone to some PR jobs on the ground. This is especially so on SQ. These girls become very marketable in the job market after leaving SQ as they are seen to have been well trained both in social etiquette or in terms of inter personal skills.
SQ female crew are recruited on a contract basis. They will be renewed if they crew maintains certain physical requirements or have been exemplary in her work. there are married crew on SQ and even those who have kids. SQ has a "flying mothers" scheme where crew with kids get to fly shorter regional routes with the occasional long haul routes so that she can strike a balance between work and family.
Of course, SQ being a totally image conscious company, requires these flying mothers to be presentable physically. You will not see overweight elderly grandmas as FA on most Asian carriers...its all about image. As far as I know, the chief crew on SQ actually has the right to tell off a junior crew if he or she feels that the junior crew is putting on too much weight (very obvious especially when u are wearing the tight, figure hugging uniform of SQ). Crew are generally asked and trained to take good care of themselves and health and especially maintaining their shapely figure that SQ crew are famous for.
There's always a better way to fly...