A woman is meant to live as free as a bird.
Granny and Sam agreed to let Panty stay in their farm, in order for her to live a peaceful and normal farmer life. She made Panty reach a resolution, often telling her that she needed to do what she liked doing the most. Granny convinced Panty to stop Corset and save Brief shortly when she resting at peace, making Panty realize that there was nothing that could stop her.In the end, everything, including her death and the mountain gang invasion, were proved to be fake and an acting. Which was all a set up by Garterbelt, in order to make Panty realize what she needed to do which is why Panty and Granny are both relatives, because she and her grandmother are angels.
Granny may have been a former angel. This is implied due to her appearance when she was young, the fact that Garterbelt knows her, and by her cell-phone, which is a Heaven GPS that the angels and Garterbelt have also.
After Panty's revelation and exit on a motorcycle, and Granny's phone call with Garterbelt, it is revealed that her real name is Tracey, which Garterbelt refers to her as.