Hello
Thanks for asking question
This is Dr Adil Ramzan
Your mother in law's age is 95 that itself is an indicator that she hasn't have much time, and now she also suffered a major
injury that has involved her brain stem, the vital point that connect the brain with the rest of the body. If brain stem die, nothing can be done and old age won't allow the damage to heal itself.
Moreover, collection of fluid in abdomen may occur due to number of reasons, but whatever the reason is, it indicates that unfortunately the major organs of your mother in law are failing.
And yes, if fluid can collect in the abdomen and make
ascites. It may also collect in the lungs. Ascites occurs when fluid leaks from blood vessels due to some problem in blood composition. If fluid leakage from vessels can occur in abdomen then it may also occur in the lungs.
Unfortunately, It's hard for me to say that, your mother in law has little time.
I wish her well.
May God bless her.
Regards.
Dr Adil