N'raac is thinking too small. My bet is for... a Divine Metamagic-based, buff, CC and sucker punch Eldritch Disciple. Unlike the Mystic Theurge, not only it's not terrible - there is no downside to taking it. For a one-level dip in Warlock, she keeps both her spell progression and her invocation progression, in addition to class features that make up twice over for what barely qualifies as a setback. Roleplay-wise, the combination provides a comfy, stylish, but harmless dark slide to her character development.
In case High Moon Elf is a must, go with a Cloistered Cleric: 18 Cha, 17 Wis, 14+2 Dex, 14 Int, 12-2 Con, 9 Str. She should stay back with the casters to provide support from behind. ('Support' in this context stands for Touch AC ranged attacks and (de)buffs. I assume we're not looking for a healbot here. It does worth mentioning that she can spam ranged healing through a class feature^^)
Otherwise, Star Elf wins by a small margin: 17 Wis, 16+2 Cha, 15 Str, 14-2 Con, 12 Int, 9 Dex. Go forth and claw some heads apart!
Clerics and metamagic work amazingly together to begin with; Still, have her take Divine Metamagic. Persistent Spell is excellent for buffing yourself and others. Add Protection Devotion to the mix if Cloistered. Get creative with the rest, sky's the limit, and her Warlock side will manage without feats just fine(though Infernal Adept IS very tempting).
For maximum effectiveness, optimize the number of dayly turning attempts. Aquire a Flametouched Iron Reliquary Holy Symbol as soon as possible, and don't forget to abuse the sh*t out of Nightsticks!
As she would be the party's spine, have her Invocation selection look like it. The party will adore her for Chilling Tentacles, Nightmares Made Real and Noxious/Incarnum Blasts. They will, however, call shenanigans if she picked Baleful Utterance. Which is to say, it's a must have. As normal Cleric, she has a choice between Eldritch Claws or Eldritch Glaive for shapes.(Or she could get a melee weapon and be done with it. I guess. But that's boring. Also, less effective.) Mind, E.C. is a feat costly road - but pays off through sick amounts of direct damage.
As Cloistered, invest in Eldritch Spear and Eldritch Chain. Healing Chain! Gods, the hilarity.
Make note of the second level spell Substitute Domain: It allows her to play switcharoo through Selune's whoppin' seven Domains like a blink dog on steroids. Take the Spontaneous Domain casting ACF or the Spontaneous Domains feat, and now she can cast 1-2x9 out of 7x9 spells spontaneously, after 10 minutes of prep for each. Add Rapid Spell to boot, and she becomes what a Binder would be like if he could make pacts for Divine Spells. No, I have no idea what WoTC was thinking. Tasty, tasty cheese.
On a more serious note, your DM is probably sane enough to whack you with the DMG, had you proposed the above. Still, the spell is pretty damn decent investment for a cleric of Selune.
Imagine as the party comes across a lycanthrope infestation, she swaps in the Moon domain and delivers their asses to them through the domain power. Need to get somewhere fast? Travel Domain. Another caster tries to be funny? Sounds like a job for Chastity. Suicide mission rears it's ugly head? Protection it is. Feelin' tricky in the morning? Night domain, comin' up. Added bonus with Cloistered Cleric - Through access to the Knowledge domain, she can double as the party's diviner, and can replace it with one of Selune's combat-oriented domains when needed, for days at a time. Yes.
