Hi Hun,
This could still be down to her illness recovery, so try not to be disheartened. The fact that she has managed a no NW night, means she is capable, so try and let that be encouraging to you. Also with any ST there can be regression, typically after a few days, you can get one or two nights where things get worse, but then often they get better than before, who knows why!? but that's a possibility.
Sending lots of ((HUGS)) and more encouragement.x.