There are a wide range of possible issues here. First, verify you have loaded the recent updated profile from Apple that ups the timeout that the iPhone uses to wait for responses from her exchange server.
Next - are you getting any connection at all to the server? I.e. does it work but still ask for the password or does it reject you out of hand when you are creating the account? If the latter, then you may have an incorrect server name or her admin may be blocking iPhones (ours did until they were approved by IT security).