Hi,
Thank you for posting your query.
I have noted your aunt's symptoms. I noted that she had 
brain tumor surgery and after that she has developed right leg weakness.
The weakness of right leg could be due to the tumor or due to 
brain injury or bleeding during the surgery.
A brain 
CT scan would help us determine the real cause of her right leg weakness.
She would gradually improve with 
physiotherapy and exercises.
I hope my answer helps. Please get back if you have any follow up queries or if you require any additional information.
Wishing you good health,
Dr Sudhir Kumar MD (Internal Medicine), DM (Neurology)
Senior Consultant Neurologist
Apollo Hospitals, Hyderabad, India
Click on this link to ask me a DIRECT QUERY: http://bit.ly/Dr-Sudhir-kumar
My BLOG: http://bestneurodoctor.blogspot.in