I have been looking around some boards and websites and ended up confusing myself more than actually answering questions!!

I am Irish, My GF is Brazilian, We are planning on getting married shortly. ( We will be getting married abroad, in the US). She currently has a study visa and works part-time. Her student visa was only renewed a few weeks ago.
My questions are :
1. Is it a Stamp 4 visa she would transfer over to?
2. How long does it take to get a spouse visa?
3. Is there a chance she could be refused?
We are looking to buy a house to move in together after the wedding so the time frame for visa, Temp stamp etc would be great help as the mortgage would be dependant on her status.
Thanks in advance.