Wrong Apple ID in App Store Sign-in Box

When I try to update applications (in the current case, iPhoto), the Apple ID shown in the sign-in box is not mine but my wife's. She has her own computers and does not operate on mine. I have checked my App Store account details and my correct Apple ID is listed as it should be. I have tried to change the Apple ID in the sign-in box but it is not allowed. My correct Apple ID is shown in the Apple Store log-in and the Apple Support log-in boxes and I have no trouble logging in to these two sites. How can I rectify this situation with the App Store log-in Apple ID to enable application updates to be obtained? I am operating on Mac OS X Yosemite 10.10.2.