"Miranda's mom was on the bus with her and got really beaten up by the crash," a source close to the iCarly star tells PEOPLE. "She's expected to fully recover, but it's scary because the driver was hurt, too, and he's in really bad shape because the injury happened close to his heart."
"This was a life-threatening crash," the source continues, adding that the driver is in critical condition after the bus collided with a tractor-trailer. "A piece from the tractor-trailer went straight through the windshield and the driver's arm was sliced all the way through."
According to the source, the people on the bus who were sleeping on the bunks in the back were not physically affected by the crash, but because Cosgrove, 18, was sleeping on a couch in the front, she felt the impact.
The Nickelodeon star was left "really shaken-up," the source says. "The paparazzi craze at the hospital has been additionally overwhelming, but she's handling the whole thing very well."
The source adds that Cosgrove, who had to postpone her tour "until further notice," and her band are tentatively planning to pick up their tour in the fall.