Look, she didn't catch the bit about him being gone so for all she knew he was ignoring her as a means to break up. You can't fault her for being mad that it appeared that the man she invested her emotions in was breaking up with her.
But, that she didn't leave her number on his mom's answering machine was stupid.
I don't blame him for actually breaking up with her in the end. Not that she didn't listen or was mad or anything--but for being so damned childish about it.