Interesting topic! Interesting problem. Can't imagine there's really anything a game developer might do--because when it comes to monsters there are probably people like my friend who might react like that to any number of monsters featured in a game.
It actually is quite the problem for me as a gamer and has become more and more of one as graphics have continued to get better and better. There have been games I flat out can't play or games where I can't get past certain parts of a game because of spider enemies. Often I have had to get my brother to get me past those parts.
I don't blame developers at all for including giant spiders or even regular spiders as enemies. I mean, it is logical of them to do so and, yes, it is impossible for devs to account for every fear anyone might have when making their enemies. It has been very nice to discover that not only am I not the only one with this problem but that there are actually people out there who are nice enough to create mods to help people with this kind of problem. Unfortunately, such a solution doesn't really exist for console games.
Thank you very much! Much appreciated!