Women

Although the question doesn't ask this directly I would first like to talk about how a women character would take away from the books. What I mean by this is that if a women was to be made into more of a drastic role I feel that it would take away from the relationship that Sherlock and Watson have created for themselves, and a women just wouldn't really fit into that. I mean we see this in the movie version when Watson is about to get married and how Holmes try's his hardest not to allow that to happen. Okay but now that I have gone on my tangent I will answer the real questions. 

The Females that have been portrayed in the book sherlock holmes to me are just fluff, they are mostly there to serve as a guide to where Conan Doyle wants that certain story to go. There is no depth or really a character background but for me they are just there to make the story flow in a certain way. I mean that is all but one.

"The Women" - now she is more then just fluff in the story I feel. Irene is much more she is the "one who got away" in sherlocks eyes. I feel that Conan Doyle did this to show that although women are not a huge part of there story that, they can still play a big part in screwing up sherlock. I feel that if Conan replaced Irene with a male character that it wouldn't have effected sherlock as much as it did. Why I believe he used a female character is because it attacked more of the pride of Sherlock then anything else. Yes he would have been mad if a man would have gotten away but since it was women it is even more of a slap in the face. I think that Conan wanted to show the audience that Sherlock wasn't perfect, and that sometimes the people who you less aspect can be the ones who make the most damage.

I think that the adaptations handle this good and bad. What I mean by this is that in Sherlock the tv show it is done better then the movie. In the tv show version, (The 2 I saw) it again used women as fluff and not that big of parts other then to move sherlock along. But in the Movie Sherlock Holmes they make Irene almost a love interest which I didn't like, so I think that they failed in that aspect to get a wider audience.