Usually the fault is the graphic card. People with AMD cards use to have problems, but many of them have succesfully resolved crashes in the past.
I don’t know which graphic card do you both have, but here are other topics that were succesfully fixed by updating the drivers from the manufacturer’s website:
Also, if you installed first with the Humble Bundle installer and then downloaded via Steam for the unstable/latest branch, it’s recommended to completely remove the Humble Bundle version first. And when reinstalling via Steam, deleting manually the game folder, not only cleaning via Steam.
Crashe reports are sent automatically through the game if you opted-in for allowing so, but if the crash happens before the game even starts, the devs don’t receive any report with your user_id.