How a green card holder get married with a non US citizen?

She cannot legally stay in the US. She will be unlawfully present and subject to removal. The processing times are currently 2-3 years for a spouse of a US permanent resident. However, if she overstays, even once that period of time is up she will not be eligible to adjust status because she will have been unlawfully present. She will then need to wait for you to become a US citizen and upgrade her status to that of an immediate relative. Only then will she be able to adjust status. Until that time, she will not be eligible for employment.

A legal resident alien who marries an alien without legal status can file petition for that spouse. Such petition is under the family second "F-2A" preference category. The current processing time for petitions in that category is about 2 and half years [30 months]. In your case, a visa for your intended spouse will become available long after her current B-2 visa has expired. And if she remains in United States beyond the expiry of her B-2 visa, [6 months], she will fall out of status. When her petition becomes available, she may be unable to adjust status [green card]. Unlike US citizen spouses, wifes of green card holders must remain in status if they wish to adjust status in United States. Because, you only recently became an LPR, it is unlikely you will be eligible for naturalization for by the time your intended spouse' petition becomes current. ( and even for about 2 years after that). You should consult with an experienced immigration lawyer to discuss in more in-depth detail various alternative ideas for your spouse that may allow her to obtain a green card more quickly or advise how she may remain legally in the US while she waits for her petition to become current.

Right now the waiting period for an immigrant visa for the spouse of a permanent resident is approximately 3 years.

She can legally stay until her visa expires. She can apply for an extension and may receive one for six month, after that she will have to leave the country. If she has a multiple entry visa, she may return at a later date.

She cannot extend a tourist visa if she is married. But if she marries 60 days after entering the US, she will be considered lawfully present while her application is being processed.