Also at the end, they plan to use the black hole to launch Brand towards the correct beacon. Not only does she have increased speed and enough to reach it in only a few years time, but the time warp from travelling around the black hole would've preserved her as well in her initial increase in time. Essentially, the time taken to travel around the black hole and Coop travelling through it ended up being equal. When she reaches the planet, she sets up a beacon and goes into "the long sleep". After that Coop goes and takes a ship and leaves to go to her.