Actually, it would be better to ask about her interests first hen
you'll know where to bring her.
If she's the nature/animal lover type, bring her to singapore
botanic garden, jurong bird park and maybe the zoo or night safari
(best if you have 50% discounts).
If she craves for food, there are many places to go; marina
steamboat, glutton bay, changi village, katong, etc.
If she's a shopaholic, bring her to our famous orchard rd or bugis
street.