Could I say that my girlfriend had sex with anybody before me?

You can "say" what ever you want.
Best thing to do would be to ASK her.

I think your question is how can you tell if your had sex before.

Asking her is important. If you do not believe her, then it is hard to tell.

Some women hymen breaks during childhood, so there is no guarantee that the lady is going to bleed the first time. Now most people think that your guaranteed to bleed the first time if a virgin but it is not necessarily true.

Does this answer your question?

If she has had sex, then she has had sex, if that is what you are referring to. Please correct me if I'm incorrect.

You can't live in the past or undo the things of the past. We can only live for the present and hope for the future.

If you fall in love with her, then it doesn't matter if she has had sex before. Unless you are concerned about her having some sort of disease because of having sex.

It would help to have more information from you in order to provide more helpful and information answers. If this is concerning some religious concern, then it would definitely be helpful to have more information from you.

It would also help to know the name of the country that you live in, in order to provide appropriate and helpful answers to you.

Actually I asked my G.F. to have sexual intercoarse with me.But she dare that if she get married with another guy then he will come to know that she had sexual relationship before with another guy.
Please tell me that she is right or not

I am 25 years old living in india.
In our country people not accepted a girl who has sexual relationship before marriage.

No one here can tell you if she is "right" for you. Only you and she can determine that. If having sex before marriage is something that is not acceptable in your country then I wouldn't have sex with her if she might want someone else.

Given your situation, I wouldn't have sex with her until the two of you are married if you are going to be honorable to the beliefs and customs of your country concerning sex and marriage.

Thank you for the private message. But, on this forum, it is bext to keep things out in the open so that you can have many opinions and viewpoints.

I only want to know that if I get sexual relationship with my G.F. and she get married with another guy.
If she will not tell him the truth, then Could her husband know that she had sexual relationship before with me?

The only way to know for certain is if she admits to it. As has been said many women have their Hymen break as children during normal play of physical activity. Worst case there are doctors who will "restore" the hymen in cultures with that sort of paranoia. Such as Muslim countries.

So nice of you to care about the next guy. If you really cared you would leave it like you found it.