All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Obeying one's parents is one of the most important obligatory acts in Islam and disobeying them is a major sin. The Prophet said to a man who came to him (asking about his mother): "Stick to her feet as Paradise is there (i.e. under her feet)." [Ibn Maajah and At-Tabari]
It is mandatory on the rich male or female to spend on his mother and father if they are poor. The obligatory expenditure is providing the parents with shelter, clothing, food and medicine. So, anything beyond that is not mandatory.
It is a form of kindness. But the child does not commit a sin if he refuses to provide it. We draw the attention of the dear sister to the fact that it is not mandatory on her husband for her mother. So, she should not spend on her mother from his property without his permission.
Allah knows best.