SSRI drugs are well known to lower sex drive. Has she tried drugs?
As always, I recommend fluoxetine. It's the longest lasting SSRI (half-life is several days), so there's no withdrawal if a person skips a day or three. It's off-patent, meaning it's dirt cheap. It's also an old drug and has a well established record of safety.
You know what's great for insecure emotional problems? Fluoxetine.
Also, sex is a physical way of showing affection. Try hugging her and touching her more often.