just ask her. If you were given a chance, would you be my lover or siblinga ?tell me why ? If she replied siblings, you got to reconider. If she answer lover, give her a smile and tell her, you think of the same way .

Hahha..at least he get the answer..but I guess this method shouldn't be pratise in this thread..haha..on a serious note, give her some hint that you want her as lover,not as mui mui..