How can I figure out the culprit with internet hiccups my wife is experiencing?
Update to latest OS X 10.10.5 and iOS 8.4. Both the updates solve the annoying Internet issues.  The issues were frequent disconnection in regular intervals, slow Internet speed etc. In Yosemite, Apple introduced the troubling Discoveryd component for networking which was the main cause. It has been replaced in OS X 10.10.4 and iOS 8.4. Install the updates and your Internet should work properly.