Quote Originally Posted by -hell_boy- View Post
After thinking for a while, I am still confused. For example, if my mother promised to buy me a cell phone and then she did not keep her word, I can say: " I'm not happy with that decision. It is not about money, but about my mother breaking her promise." Then we can understand that I am not happy with "my mother breaking her promise" not "my mother who breaks her promise." Is this because of the context that we will understand the sentence?

If you take I'm not happy with my mother breaking her promise out of context, the meaning is still clear- she broke a promise. My mother breaking a promise is more likely to be a one-off, but my mother who breaks her promise/promises sounds like a character flaw rather than a single instance.