OT: Female libido, arousal and response to sexual advances.
"It's not you, it's me. I just don't think about it unless you've inspired me to"
So inspire her. Use your skills to make her feel special.
Then, under other circumstances, communicate to her in a nonthreatening way that you too deserve to feel special and that is something that you will appreciate her for when she is able to reciprocate.
Don't make this a "tit for tat" exchange (i.e. "I do this for you so why don't you do this for me.") discuss the issue in a way that makes you both feel like you can grow closer by working out this sticking point.
Nuff said by the shrink, usually free advice is worth exactly what you paid for it.
BTW, Dew's solutions (Adderall or testosterone) may work for some, but there are significant side effects, none the least of which are either a sleepless night or facial hair growth, neither of which work for many women.
aj