If your love thinks that a hormone imbalance is causing her lack of sex drive, then I wonder why she isn't doing something about it. The fact that she isn't taking steps to address her problem tells me that the lack of sexual desire isn't a problem for her.
That would be fine if she weren't with a partner who wants more sexual contact. Since she is in a relationship, she needs to own the fact that her inaction is a communication to you, which leaves you to feel dropped and not cared for.
In other words, she is saying,'screw you' and she needs to take ownership of her behavior and then put the feelings that she is expressing in action into words. 'Screw you' behavior is the result of angry feelings that aren't being said.
I want to know why she is mad at you and why she feels like not giving to you. What are you doing or not doing that is pissing her off.
If you can get her talking about her feelings toward you, you are half way there. Your talks may reveal that there are other, nonrelationship issues troubling her. She may be depressed or stressed. She may also have mixed feelings about being gay and you may be getting the fallout.
However, don't be fooled. There are more than individual issues afoot here. So, focus on getting at the underlying feelings and the symptom of these unexpressed feelings (the lack of sexual activity) she resolve by itself.