Rosen,
Welcome. After what I read your mum is probably de-hydrated. I had to learn it the hard way, but most people don't drink enough water me too. When I was in the hospital after my stroke, the doctor just said it to me and did give it another thought. He told me "your are de-hydrateded" and never said another thing about it.
So i researched when I could (it took a long time). But I found that our brain is 98% water. So it makes perfect sense. I try to drink as much water as I can. And I bet your mum's constipation will go away if she starts to drink water. Make her drink some water everday. And if she is still constipated then you can sue me.
God Bless you,
Tim