How to know whether a girl is virgin or not if she do not tells us ?

Ask ? There is no real way to tell except from what she says. At the end of the day, it is never what she did before, but the relationship you have together now.

Please do not ask the same question over and over. Your other post has been deleted.

If she wants to tell you then she will, the past is the past for a reason.

Honestly it should not matter that much. As far as STD's maybe but other than that Rome said it all the past is the past for a reason. I'm sure we have all done things we are not proud of.

Why do you need to know? How long have you two been going out? What grade are you two in? How long have you two been bf/gf?