My dad had secondary cancer originally from the lung in his brain in January (he had the tumour removed) his mood changed from then, he was a kind friendly man before. After he was very outspoken and sharp, but we are the kind of family who laugh at things and joked about it.. He had good days and bad, days where he got up and walked and ate and says where he refused food and wanted to go to bed. We encouraged him to stay out of bed and sometimes forced him to eat by bribing him with things that he did like, it was like having a small child. Unfortunately he grew worse and good days were few but we still carried on with a normal life with him, which is what he wanted as we discussed it before things got worse. After a spell in hospital in early July he came home and he deteriorated spending all his time in bed but we carried on making his room the main room we sat in and included him in everything we did. He knew who we all were even if he couldn't remember our names at one point I was super charge and worthy! I've no idea who what or why he thought I was that but it was amusing and the look of disgust on his face when myself mother and daughter laughed made us laugh even harder, eventually on  25th of July he passed away, that day he didn't wake up at all but as normal we sat with him talked to him joked about things that he had done we had done events etc I know it may sound strange but I know he could hear us, he passed peacefully no suffering exactly how he wanted at home in his bed. Even after his passing we sat with him and talked to him.  My advice is carry on as normal when I say normal I mean treat your mom as you would normally laugh joke reminisce and enjoy what time you have take each day as it comes good or bad. I know it's difficult sometimes. I too have lung cancer and I don't have much time but if I go like my dad then I will be happy.  

Normal doesn't really apply at this stage but it isn't unusual for this to happen.

Our mental state has an impact on our physical state, so I guess it isn't a surprise that your Mum feels better now that the anti-depressants have taken the edge off her anxiety. 

Enjoy this respite as best as you can and make some happy memories with your Mum.

Best wishes

Dave