Jim Douglas at 2015-07-01 20:27:13:
I think it's worth pointing out that Joe didn't create a female character, he created a plot point. Without knowing the character's role, it's hard to fully judge, but adding a love interest because the script needs "more of a female presence" is one of the more obnoxious tropes out there. If the character serves a purpose in your story, by all means, add them in, but I suspect there's an easier route to interesting characters that Joe could take, one that may be staring at him right in the face:
Make the lead female and your "added" character male. Now you have a much more uncommon dynamic.
Rare is the instance when this would be unrealistic or unreasonable (maybe if the protagonist is a professional baseball player or something), but there are so very few good roles for women in Hollywood that top actresses will sign on to play the standard "girlfriend" or "wife" character that acts as a one-dimensional voice of reason or carrot-on-a-stick for the main character simply because there's nothing else out there. Heck, this might even be your selling point; if it's a juicy role, send the completed script to an actress trying to break out and let her do the work of selling it around town for you.
Scott's mentioned this on this site before, but it bears repeating - one of the easiest ways to spark creativity is with a gender switch. If it doesn't work to switch the main character, switch one of the sides. You don't have to add, you can consolidate. How would switching the gender of a prominent character you already have written affect everything? Should it affect anything? Are they a woman in a man's world? Do they overcompensate for having to live against the grain, or do they just go about their business and let everyone else worry about it? And on an on...
If your story is great, you can usually and more interestingly create female presence by changing gender than by adding unnecessary characters. I'd suggest starting there - it might help.