John stared, but otherwise didn't make any move to prevent her from leaving.
The Doctor held tightly to her hand and tugged Bill toward him, into his arms in a firm embrace to hold her steady. Then, closing the TARDIS door, he paused to examine Bill's dirty, bloodied face.
"This is the best place for you to be," he told her, meaning inside the TARDIS and not the hospital, but it also suggested that being with him was also the only choice. "I'm taking you out of here, and to the the TARDIS's sick bay." He walked with her, giving Bill support down the ramp to one of the chairs positioned around the edge of the console room floor. Wait one moment," he told her, then went over to the press some more buttons before starting the engine that got the time machine working again.