1) I would avoid using the word "free" in your adcopy.
2) Like someone had mentioned above, get some merchant insight into how they determine "quality". Most of the time it's how many leads convert into a paid subscription, but depending on the offer your advertiser may be looking at something else.
3) Are you targeting 18, M? This could be your issue right here. Sure it converts great for you, but those leads are worth nearly nothing to the merchant. Shoot for 30+ women even if that demographic is not profitable for you.
4) If you're using a landing page you could always use verbiage that will push the user to where you want them (ie to convert into a subscription). Sure not every lead will convert into a sale for the merchant but if you can get 1 out of 10, I'm sure they'll be happy with your "quality".