I will add that she has told me that she is completely clean and healthy, and had never cheated on her husband before.
Test at 8 weeks for a good indication, 3 months for conclusive.
Can't really give you stats or make an assumption on what you have said.
Any knowledge about the Visa and HIV policies in the US?
Nope, best advice is to google it.
I don't believe that HIV testing is required to obtain a visa, but like vance said, if you google it, you could find out for sure.
We don't really play the "numbers" game...we assess based on either a person had a risk or did not. You had a risk.
A NEG test result at 6-8 weeks would be VERY strong evidence that you did not get infected, but a follow up at 3 months is needed based on current guidelines for a conclusive result.