Legal Question in Immigration Law in California

Overstaying is considered a serious violation of the law. If she overstays between 6 months and one year she will be inadmissible for 3 years. If she overstays for more than 1 year, she will be inadmissible for 10 years, even if you were to marry her. There are certain exemptions which cannot be discussed in this limited forum.

There could always be problems with any immigration case, such as criminal issues, perceived fraud, immigrant intent, etc.

However, in general, if a person who is admitted to the U.S. on a visitor visa, & overstays, then marries a U.S. citizen later on, can file for adjustment of status, based on marriage to a U.S. citizen. However, any bars to adjustment are another issue.

I would recommend having an experienced immigration attorney review your girlfriend's case, if you eventually get married, or intend to get married later on, before you file her I-130 petition/I-485 application.

Good luck!