A larger monitor will make things bigger. 100 letters sized across 21" are going to be bigger then the same letter across 17". But unless she gets a HUGE monitor, it will probably not be enough.
Try adjusting the screen resolution. Right click on the Desktop and select Properties. In the window that opens, click on the Settings tab. You will see a slide bar in the center left. If you move that bar to the left (so the numbers get smaller) everything on the screen will be larger. But you will also see less of each page and may have to scroll around more.
Within Internet Explorer there is a method to increase the size of things just within Internet Explorer. IF you look in the menu under View, there is a Text Size option. You can change to a larger text size. (You can also change the text by holding down the CRTL key and turning the scroll wheel on your mouse).
Finally, Windows as a program called "Magnifier". From the Start Menu go to Accessories and then Accessiblity. You should find the Magnifies there. When running, it opens a sizable window that magnifies any part of the screen you want for you. With a little practice, she should be able to scroll her cards under the magnifier and make them much larger so she can see them.