On a Mac, can you navigate menus with one handed key strokes like Windows?

On a Mac, is there anyway to navigate menus with one handed keyboard strokes like you can in Windows? My girlfriend is a graphic designer and switched from Windows to Mac. She misses being able to use the Alt key and make menu selections. On Windows she can press "Alt" and then move through menus and submenus with one hand on the keyboard. When you press "Alt" the first letter of every menu is highlighted. When she presses a certain letter the menu drops down, and the first letter of every submenu is then highlighted. She can then navigate through all the submenus until she hits the selection she wants, all using the left hand on the keyboard. It's very fast and efficient. Can you do something similar to this on a Mac?

The reason she wants to do this is because when she is in Photoshop, she likes to use her right hand on the mouse with the cursor inside the canvas (sketching, moving layers around) while she makes menu commands with the left hand. It is 10 times faster this way than using the mouse for everything. Hot keys are not the same because you must have those memorized. With the "Alt" key function, you can open a drop down menu, see the choices, and make your selection.

I have been a Mac person my whole life, and I have to say, it's a pretty awesome function. I really want the Mac to have something similar.