It is always a good idea to discuss your specific situation with a lawyer to make sure she is eligible to receive the K-1 visa and eventually immigrate to the US.
If you were to marry your girlfriend she would not be eligible for the K-1 visa, but she may be eligible to immigrate to the United States in another way. The strategy is complex if you have not done this before.
A K-1 visa can only be issued by a US embassy or consulate so your girlfriend would have to complete the process in another country. If your girlfriend had another type of US visa which allowed her to come to the US in another legal status, then she could be in the US in that status while you were waiting for the government to process things. But she would eventually have to go abroad to complete the K-1 process.
If you have any questions regarding immigration, please feel free to call me, immigration attorney Shawn Mesa at (813) 679-5780.
Disclaimer: This information is provided as a public service and not intended to establish an attorney-client relationship. Any reliance on this information is taken at your own risk.