Is it normal for a 14 year old singaporen girl about the height of 145 not started her mensturation yet?

Maybe,maybe not: If there are signs of puberty present (breast development) there is a chance this is normal. 1-2% of girls start at 16. Most would have an evaluation done if this has not occurred by 15. The girls short stature <<5% brings up concern for other conditions that might be important and i would seek out an evaluation of her short stature & developmental delay now rather than later.