Routing the call externally will work (if the calling of the companies own DID numbers by internal numbers via the PSTN is not prohibited in the digit conversion tables), but has a cost issue.
Routing to the secr extension with coverage y in the vector might work but there was something with double coverage... Since the call was already covered from the attorney's phone it could be that the call is not following the coverage path of the secretary. Instead the call will keep ringing on her phone.
If however the above works to your satisfaction please stop reading since you have already found a good solution. If you are intrested in another suggestion. keep on reading.
What you could do is putting the secretary's extension on point 1 of the attorney's coverage path (I believe it's already there). Point 2 of his coverage path could be a VDN with a vector that has a "messaging-split xx for extension yyyy" step in it. xx being the voicemail huntgroup number en yyyy being the secretary's extension.
If the secretary is busy, does not answer, or has SAC activated the call is covered to point 2 and that is the secretary's mailbox.
Let me know if this was helpfull.