According to Google, "Functional neurological disorder (FND) is a medical condition in which there is a problem with the functioning of the nervous system and how the brain and body sends and/or receives signals, rather than a structural disease process such as multiple sclerosis or stroke", but that obviously doesn't clarify what it like for the individual and those close to them what it's like to live with. I know she picked the wrong day to test you, but you're both going through something very difficult, so my advice is try to be patient with her.