Check the email account properties. (Go to tools, email accounts, leave on “view or change” then click “more settings). On the security tab, make sure “Always prompt for logon credentials” is not checked. It sounds like she is getting prompted on every send/receive.
Check also to see if the user is setup to use RPC over HTTP. We have seen this create authentication issues if not enabled at the Exchange server.
What path do I take to verify on the client & then on the server?