Need some answers

I dont know where to begin.... its been a few months since my mother got diagnosed with Lung Cancer that has spread to her bones. Her left lung colasped. She's with only one lung currently. Yesterday when she went to the doctor to do her weekly draining they barely took any out. I don't know what this means. It actually scares me. My mom isn't one to talk much about it. So i feel lost. Does anyone know what it means when your used to getting a weekly draining to just one week not have anything to drain? I'm the kind of person who needs answers.

Thank you