My girlfriend was married?

I have a difficult situation I figured out, that my Japanese girlfriend was married in past with one Japan man. So shorty, she explained this that: That this married is invalid it's mean without any matter because they want take marriage but after this man said no so after 2 week them "marriage" she taking back paper or cancel from office and in office they said to her that this married is invalid coz for be valid must be longer than two or three months(don't remember now) so she is still "miss" not "Mrs" or "divorce". But she said that she after this married change surname and after cancel paper back to old surname . Here is my question this is possible?? Or it's just lie?

Many thanks for reply

We don't know your girlfriend.... Talk with her about your problems.

If she tells you that's what happened, you should believe her, it's your girlfriend after all.
If you don't believe her, or if she's lying to you and you trust internet strangers more than her, you have bigger issues to worry about in your relationship, I think.

It is theoretically possible. Are you from a country that prohibits second marriages?

Marriage can be cancelled in case the woman was under 16 or the guy was under 18, or if the marriage was under duress or threat or fraud, or if one of the parties was already married to someone else. In that case it can be cancelled within three months.

If you have doubt and don't believe her, then go with her and get her koseki tohon at city hall to checkout/confirm her story.
The koseki should list all her marriage/divorce history if any.