Difficulty walking due to leg weakness

[psc]

Hi,

My mother is having difficulty walking due to weakness in her left leg. She can move her leg sideways but cannot lift it. Her oncologist had a brain, spine MRI done. They gave her conformol (3D) radiation for 10 days on the back side of her head for the brain metastases. However there hasnt been any improvement.
- Radition onclogist feels that the spine has a few spots but he desnt think that is the cause for her leg weakness. He said sometimes there is a delayed response to brain radiation. Is that true ? He said that we could try giving radiation to the spine though.
- Her oncologist wants to put her on chemotherapy.

She was able to walk until 15 days back. I am feeling very bad - she has gone through so much already in the past 2 years, I have tears in my eyes everytime i think about this...
What is the best option to treat this? Does anyone have similar experience? Please help

thanks,
psc
Dx Mom, Stage IV, ER- PR-, HER2+