For bullets/attacks, she'd need to go to Options > More Options and change Enemy Attack colors to the one that makes them most visible to her. I imagine that's the main concern.

If she wants to see the sprites better, someone (including you, if you want to take up modding) could run all the sprites into a red-green colorblind filter and made a cosmetic mod so your friend could see what can be changed through the current API, but otherwise most visuals are untouchable.