Hi botanyao,
If you can provide us more details about your sister, forumers here
may a clearer idea on what kind of advice she'll need.
***
If I'm not wrong, there is no age limit for abortion in Singapore,
but if your sister is below 16, she has to undergo counseling
before obtaining a certificate.
Only with that certificate can your sister undergo legal abortion
in Singapore. For this she should go to the Health Promotion Board
Counseling Center (6435 3143).
***
The level of danger increases as your sister's pregnancy
progresses. How far along is she? Is she 3 months or 6 months
pregnant?
What about your dad or mum? Abortion costs can range from $300 -
$2000. Where will you guys find the money? Who will be the best
person to take care of your sister when she is weak and recovering
from the procedure?
These are the questions you might want to think about before you
take any action.