This is awesome stuff, especially if I was planning on making a divinely converted succubus (a succubus version of a redeemed lich, per se) but I don't think the story allows for that kind of drastic changes.
I wasn't sure how "holy" you were making her, so I figured I'd go over everything.
The energy drain and profane gift* are a bit more tricky, though. (*Where do you see profane gift? I'm looking at the 3.5 MM and the SRD and I'm not seeing that.) The energy drain seems to be a racial thing- Succubi can choose to draw sustenance in the form of life energy from people they kiss (or more.) If you look at it a certian way, this isn't a taught thing- it could be similar to Rouge's energy drain ability- it's just a natural thing that they can't control. Turning that into a positive energy ability would be altering the very being of the succubus- which would probably require lots of divine energy/intervention and probably a lengthy ritual.
I sourced it off the Pathfinder SRD, 'cause I always mangle Pathfinder and 3.5 into one big mish-mash in my games. Pathfinder has a lot of nifty fixes to stupid broken things in 3.5, at least in my opinion.
Succubi gain a resistance to spells- makes sense that she'd keep that, as her outsider/demon type remains the same.
They also gain Fire/Cold/Acid resistance 10 and Electricity/Poison immunity. How much of this could you say is a result of racial strengths, and how much would be a result of the horrendous tortures and trials that a young demon must go through to reach maturity in the abyss?
Depends on your perspective, but I would leave them alone, mostly for simplicity's sake.
I do think that the natural summon demon ability should go- either because she is unable to name any demons to call, or because she never learned how to do it in the first place.
The church could have taught her how to call upon the power of good-aligned creatures. But it's not a huge deal.
Basically, I'm trying to see what I can do to strip a level or two off of the CR of the Succubus and make it feasable to be introduced as a neutral-ish NPC, under the storyline logic posted above. I will take a look at the SS level increments, but by the time that she's showing up to break the party free, I'm hoping that she's going to be high enough level to have gotten through her racial leveling. (Which is a bit brutal going through the SS version of the Succubus levels, as seen from a previous thread about succubi leveling.)
Racial levels...bleh, kill me now please. Highly creative but really one of the most horribly under-powered, unbalanced things to ever come out of anything.
Here's my opinion. She's an NPC, she can be literally WHATEVER you want her to be. Even if call her a "succubus" that doesn't mean she actually has to BE a by-the-book stat succubus. Not to mention that a CR7 Succubus is intended to be a challenge for an entire level 7 party of 4-5.
IMO, don't make her a succubus. Make her
YOUR succubus.
I mean basically a succubus is what, a human with some super-natural abilities right? Flight, Energy Drain, claws. +2 cha, +2 dex -2 con(by pathfinder rules anyway), that's not really all that spectacularly more awesome than most 3.X races. You can basically take the tiefling template and call it a succubus, then just slap a class on her, maybe an extra power or ability and run her as a special NPC.
Really what is a succubus if not just a hot woman with wings with the magical ability to pleasure someone to death?