So a classmate broke the headstock on her guitar, and wants to know if it can be fixed. I know some kind of glue can be used, but what? It's an acoustic btw.
Let a luthier do it. A good luthier will know exactly how to do it, which includes clamping, getting the right amoutn of glue, using the right kind, and positioning it correctly.
Might cost a fortune to get it fixed, if it's a cheap guitar, you'd be better off getting a brand new one anyways