Calendar Invites not showing event on Calendar after accepting?

I was hoping someone might be able to help me. All day at work I send and receive requests in Calendar with no problem. My Wife sends me them and they come through as iCloud Emails, I press accept and they don't save in my calendar. Is there something I could set on her iPhone that will have her request come through like everybody else? She has an iPhone 5 and uses Gmail and iCloud for her Calendars and Contacts.

Any help would be appreciated, thanks.

Thanks for the reply, I'm using iCloud.

She uses iCloud calendar and gmail for email. I use iCloud calendar and iCloud email. My clients and coworkers usually use exchange servers. I have some clients that use gmail emails, but I don't know what they are using for calendars. When I get invites from anyone it usually comes in directly through my calendar and I can accept and decline directly in the calendar app. My wife sends it and it comes to my email, and it never displays at all in my calendar at any point.