Murris has an error message that says she's out of application memory and she had to do a hard reset to get it back. Leo says that's called a hard crash. Murris should always make sure she keeps it up to date with OS updates and patches. But chances are, Murris left something on in the background and it may have crashed which caused it.
It could also be what's called a "memory leak," where an app doesn't free memory when it's done. Leo suggests opening up "Activity Monitor" on the Mac and it will tell her what's going on and what's using the memory up.