Most likely due to economic status, affluence, and the social
context in which they were raised.
This applies not only to women but to men as well. For example,
people from different states in Malaysia have very different
mentalities. A kid raised in KL would likely to be more affluent
and more street smart than someone raised say in an ulu place like
Sarawak. The attitudes toward studies, friends, relationship etc is
totally different.
Singapore is a very affluent place. The girls are exposed to the
best their parents can give them , and this is usually much more
than most Malaysian girls (except for those from KL). Of course
they would be much more worldly, mature and openminded compared to
some girl from a primitive country like Indonesia who has lived her
life 'under a coconut shell'.