Who needs party members, when the succubus you spared and recruited can just absorb your enemies knowledge, right?
That's totally not your morals melting away together with the groups' healer in there.
The priest girl definitely had it coming for badmouthing your girlfriend, telling you how "demons can't be trusted".
Just forget about her and fuck the succ, while she digests her meal.
If you are a good boy, you can slide down her tail or throat later and enjoy soaking in her aphrodisiac juices again.