OWA user unable to send or reply to emails.

Does IE shut down when she tries to reply?

http://support.microsoft.com/?kbid=924334

I have seen this twice. Once caused by a CSS issue and the other by 128 Bit encryption on the Back end servers.  Both issues caused a break in the authentication from the OWA to the Mailbox server.  Are you seeing any errors in the logs on the Mailbox servers?

Another possibility is if you are hosting Exchange in a resource domain.  If her user account is in another domain and you are using Associated External Account priveldges make sure those are correct.  Basically she needs to have send and receive permissions on her mailbox account.

This is a user on her home computer.
I am pretty confident that this is a client issue and not server side.

I was able to login in remotely last night no problem.
I have advised the user to update her computer, service packs, etc and disable pop up blocker and firewall.

Stupid question, but what browser is she using?  I have had issues with specific versions of FireFox and Google Chrome throws up on Meeting invites.  Also, speaking of meeting invites...if the first message in her mailbox is a meeting invite (or that is what she can't work with) then it could be related to the cdo.dll on the Exchange servers being out of sync.  I have seen that before...

She is running IE

Apply the hotfix that I posted above. It fixes issues with OWA and Internet Explorer 7.

I would agree.  It would also ensure that the dll versions are the same.

Oh... and do the Front end first, then the backend.

Server is already patched.

Did you try the user's account from another client?

I am the admin here not at home, it worked, IT gets rolled over too much and when something is broken its  always IT's fault.
Hope she likes geek squad :)