Drive Mapping

Is the server she can ping/map the VPN server, or is the VPN established via a router.  If so might the remote network be the same subnet (network ID) as the server.  E.G might they both be using something like 192.168.1.x ?
The two sites need to use different network IDs.  If the same you can often connect to the server if "use remote default gateway" is selected, but you won't be able to c0onnect to anything else.

The other though is when you enable file and print sharing on a server it also creates a firewall rule to allow connections, but only from the local network.  You may have to add the remote subnet from which the client is connecting.  As a test, disable the firewall on the problematic server.

She is unable to ping the file server in question or the NAS. It was working fine until recently. She can ping the SBS server.

If her local subnet is the same as the SBS server which I assume is the VPN server then that is exactly what will happen.  Might both be using something  like 192.168.1.x ?  If so, one site or the other will have to change.