There is something stopping the updates, the latest is 100722-1 released a couple of hours ago. Try a manual avast update.
The one in the dllcache location is a backup one so shouldn't be in use. The one in system32 is a system file and avast won't send that to the chest or delete it (and you shouldn't try to remove it either), so you should select No Action.
What avast version are you using 4.8 or 5.0 ?
What browser is she using as I believe this is related to IE using ntdll.dll, so you could try installing firefox, download on your system an transfer.