If a US green card holder marry a Canadian citizen will she become a Canadian citizen?

No. Assuming that there are no other legal impediments to your entering Canada, you could get into Canada. You could apply for permanent resident status - something you should do BEFORE you arrive in Canada. Being married to a Canadian citizen would probably be a big advantage. Getting Canadian citizenship is a whole other process. Before you can apply, you have to have lived in Canada for three years without interruption or, in some cases, for three of the last four years. If you meet all of the requirements, THEN you can become a Canadian citizen. Being married to a Canadian will help with that. But marrying a Canadian will NOT automatically make you a Canadian citizen.