What version of the OS is running on the iMac? (Apple menu in the top left - About this Mac) It's likely to be a name of a large cat if it's older (Snow Leopard, Lion, Mountain Lion), or some California place (Mavericks, Yosemite).

What web browser is she using?

Is Flash installed? If so, what version? (If she's using Safari, check the Help menu for "Installed Plugins" to see if Flash is listed. If it's Chrome, Firefox, or another browser, typing "about:plugins" into the URL bar should also show if Flash is installed.)

Also, a common Mac troubleshooting step is to isolate the problem to her user account, or the machine in general. To do this, follow these steps:

• Go to the Apple menu - System Preferences
• Find Users and Groups - usually in the bottom left
• Click the lock in the bottom left, and type in the password to unlock
• Click on Login Options, and check "Show fast user switching menu as".
• For the dropdown at the end of "Show fast user switching menu as", set it to full name.
• Click the plus located below the Login Options button and create a new user.
• New Account: Standard is fine, full name and account name could just be "test".
• You may need to first select "Use separate password" before being able to set the password to "test" as well
• Click Create user

At this point there should be a new item in the menu bar in the upper right with her full name. Click on that and pick the test user. Type the test password in, and you should get a new user login screen. Try opening the browser there and seeing if the same issue persists.

When done testing under the other account, go to the Apple menu in the upper left, and pick "Log Out Test" at the bottom. You should then be back at a log in screen and can return to her account.

Answering the 3 questions above and doing the separate user test will help narrow the issue down a lot.