It is clear that the title of this excellent short story is symbolic in a number of different ways. Firstly, you are right in identifying that it refers to the various literal leaps that make up this story: the leaping that her mother used to engage in when she worked as a trapeze artist, her final, fateful leap that she managed to change so that she landed on some heavy wire, and then her final leap down to save her daughter from their burning home.
Yet, apart from the literal instances of leaping, there appear to be two specific "leaps" that are much more metaphorical in nature. Firstly, we have the narrator's mother's second marriage, which is described by her daughter as follows:
I wonder if my father calculated the exchange he offered: one form of flight for another. For after that, and for as long as I can remember, my mother has never been without a book.
The literal leaping is exchanged by Anna for metaphorical leaping or flying of the imagination, as Anna finds new worlds opening up before her thanks to her newfound literacy.
Secondly, the narrator herself has made a leap from her "failed life where the land is flat" to come home and look after her mother. We are given no more information about the nature of how the narrator has failed in her life, but it is clear that coming back and looking after her mother has given her the excuse she needs to make a leap in her life, closing one chapter and beginning a new one.