I don't like the USA system. The UK process, for example, is much better; all the evidence to support the application is uploaded and the ECO has everything they need to make a decision. With the USA process the online submission is basically just static data collection - nothing to support financial adequacy or reasons to return - just about enough to establish a genuine reason to visit.
It would appear that everything rests on the 'interview'. Having now spoken with the applicant she seemed to indicate that they didn't even look at her folder of supporting information. Whilst I find that incredible, if true, it is what she said.
The arrogance of the system is highlighted by the published assumption that all applicants want to be 'immigrant' applicants and their application has to first prove that is not the case.
If this lady was a British citizen, with EXACTLY the same financial situation and same ties to the UK, she would get an online visa the same day. But because she is Thai she has to go through this farcical subjective process - that is as close to modern day discrimination/racism that you can get.
That is bull<deleted> - not from you but from the USA authorities. She is not single (that bit was bull<deleted> from you) but in a domestic relationship akin to marriage for 10 years. She is a 50+ year old Thai citizen who will never live anywhere but Thailand.
If UKVI consider her suitable for the granting of a visa then that is more than good enough for the USA authorities.
My friend will give it one more shot but I fear that the applicant will not have the confidence or skills to do well at the interview. To me that says more about the USA than the applicant.