How do I stop receiving calendar invites on iCal/iCloud and use exchange 2013 calendar instead?

Question

I Have an exchange 2013 email account which isn't registered as part of my iCloud account.
i Use my outlook calendar (exch) for work and the same exch calendar day to day from all my iOS devices.
when a colleague or outside email away from my company sends me a calendar meeting request, it works fine. (Using my exch email as the invite recipient).
my girlfriend sends me a meeting request from her hotmail account using the same exch email address for me, but he. Invites always arrive to my iCloud/iCal calendar instead! I can't seem to change it so I often miss diary notes or reminders unless I constantly look at both calendars.
i Just want to use exchange calendar and lose iCal (or if easier sync both iCal and exchange calendars vica versa - but that may be over complicating the issue, basically I just need one calendar and would rather it be my outlook exchange cal)
any ideas?

Answer 1

Hello again,
False alarm..... it didnt work sorry.
I removed the iCal accounts from my mac, and also from my iphone. Then when my partner sent me a calendar invite it simply didnt arrive at all!
She has a hotmail account installed on her IOS iphone 5.
She is sending the invite to my exch 2013 email address which is not associated with any icloud account.
My exch 2013 email is installed in both my Outlook for mac 2011 and IOS device Iphone 5s.
When I switch the iCloud Calendar back on in my iphone 5s, the invite comes through but ONLY optional to the icloud calendar. I cannot seem to get it receiving on my default calendar which is set to Exchange 2013 account.
Its very strange as its only her invites that do this. Anyone else's come through on my exchange calendar because its the same email address receeving it my end.