u/wafercak

I’m going to start this with saying I’m literally clueless about bikes and need some help. Bought this used GT mountain bike for my daughter TODAY, took it for a ride, shifted gears and then this piece just snapped off (I presume the shifter??) literally just busted right off and is now completely broken. Is this repairable with a new part? Can you even get parts like this? I’m so disappointed as is my daughter. Please help!