You're pissed about something she has absolutely no control over? Please. That doesn't make a lick of sense.

The Pill can cause dryness. That's a classic side-effect of any hormonal birth control. Fluctuating hormone levels during the month can. Nuva-Ring can. Dehydration can, like when a person has had too much alcohol and not enough water. Even having sex with a running ceiling fan up above can aggravate dryness. It's certainly not just caused by too little arousal, but if your ego is so delicate as to feel you're "being kicked in the gut" because you believe otherwise, then the real solution here is to stop having sex immediately and get some therapy for yourself.