Meeting Changes Don't Work and Multiple Entries Show Up

I have a user that has a bit of an issue with her Calendar. There are
times when she's sent a meeting she will see it several times in her
Calendar during that timeframe. One will be accepted and the others are
marked as Tentative. Another issue is if I send her a meeting request for
say 10 o'clock but changed it to be 11 the new meeting shows up and the old
meeting stays resident as well. It doesn't auto delete.
She does have a couple of email boxes she administers. Could this
have something to do with it or has anyone else seen this and what did you
do to fix the issues my user is experiencing? These other accounts that she
admins - the Calendars are not tied to one another but thought I'd bring it
up anyway. Can it have an impact here?

Any help would be greatly appreciated -

Jon