You should talk with your local US embassy or consulate. They can provide whatever help to clear up the process for your partner. If they are doing their job, they can greatly simplify everything. Please do not confuse the local state dept people with the shenanigans from the people at the White House...

The visa process is relative straightforward. Will the person who is given the visa come back to the country of origin? This is determined by money more often than not, and it's the harsh reality of the situation.