what is the common expresion of girls when someone proposed them ?

For Filipinas it's usually "ewan" ( I don't know) or just a giggle or a shrug, or silence. Of course it depends on the personality of the girl, for the more vocal, they could reject the suitor at once when they don't like the suitor, but if she likes him, he'd be in for a big surprise. Of course, the "ewan" is just a euphermism for "yes" or a "no". Filipinos are not so definite because they want to maintain SIR (smooth interpersonal relations). That's why one should understand the culture of the girl in order to really understand what she is saying or trying not to say...well, you know girls...they said we are fickle minded, but that's the way it is....