Grace is the Major's rebound woman. The town ladies always tried to meddle in his affairs and set the two of them up, but it was just too awkward. However, the two are forced to work together when the Major is assigned to be on the food committee for the annual party, though the Major only agrees in order to get closer to Mrs. Ali.
The Major and Grace would be a good fit. She's nice and traditional, as he is, and she likes learning about the town's history, which he would like to preserve. She's a good friend to Mrs. Ali, and even lets Mrs. Ali borrow a nice dress. In exchange, Mrs. Ali lets Grace borrow a sari.
However, the Major just isn't interested in Grace. He wants Mrs. Ali. When Mrs. Ali leaves after the racist party, the Major and Grace spend time with each other, both having lost their mutual friend. Eventually, the Major sees everything we just said about them being a good match, and he asks to start a relationship with her.
Request denied! Grace shoots him down faster than he shoots down a duck, saying something that is quite true: there is no passion between them. The Major thinks being old means they don't need passion, but Grace disagrees: "There is only the passionate spark. Without it, two people living together may be lonelier than if they lived quite alone" (20.38). The Major comes around to see this point. He and Mrs. Ali have passion, and they're able to explore it without throwing their backs out.