Yes - this is the the most difficult time of all. The radiation continues it work for several weeks post treatment so it is no surprise that she is still on a downward spiral. The good news is that she is right at the turning point. Remember that progress is measured in three week increments at this points - in other words verrrry slow. It takes much patience to get to the other side. This is also when depression most commonly sets in.

The mucous thing should resolve pretty quickly.
Some people have had some luck with various decongestents.

She has to eat - she needs nutrition for faster healing. I had to force myself to eat. She'll feel especially crummy if she gets dehydrated also.