OK, some synergy there and there's a concept to work with.
The blackened curse does add scorching ray to your list of spells known which may be useful, but -4 on weapon attacks is a pain. Hellbound might explain your fire problem, and immunity to fire at 10th level might be handy. Legalistic might explain your curse the same way hellbound does but it comes with an insignificant downside (and less benefits, them's the breaks).
I still suggest spell focus and spell specialization, you've got enough of a point buy that 13 Int isn't a problem, and spell spec. is pretty good.
You could get a trait which reduces the cost of metamagic - useless to you now, but it'd help later. Or the elemental accident trait certainly fits. Or reactionary will always be useful, sure.
Just pure fluff, the curse "Cold-Blooded Lizardfolk" fits perfectly (even if she's not a lizard, she has scales and stuff, maybe a Naga in the bloodline?):
Your blood turns sluggish without sufficient heat, and you must seek warmth and shelter earlier than most. This oracle curse is common among lizardfolk and other oracles with the reptilian subtype.
You take a –4 penalty on saves against cold spells and effects, and whenever you fail such a saving throw, you are staggered for 1 round. You can survive without food four times longer than a typical creature of your species before you begin to starve.
This curse basically requires her to seek fire just to survive, so it's not so much the water magic she has trouble with but the cold that comes along with it.
The benefits of the curse work well with the Undine's Steam Caster feat:
At 5th level, poisons affecting you have their onset time doubled and last half as long if they end after a set time (for example, a poison with a frequency of 1/round for 6 rounds would instead have a frequency of 1/round for 3 rounds). Poisons with no onset time gain an onset time of 1 round.
At 10th level, whenever an action you have readied is triggered, you can take an additional move action at half your speed—along with your readied action—even if you have already taken a move action that round.
At 15th level, you can take an additional move action a number of times per day equal to your Charisma modifier. You can take these additional move actions only on your turn, and can take only one of these extra move actions per turn.
Steam Caster turns a spell into a full-round action, consuming the move action along with the standard action to cast the spell. The 10th & 15th level curse benefit grant extra move actions to offset these costs.
Maybe ask the GM to have the 5th level benefit replaced with something more fire-themed, like the fire spells from the Blackened curse.
Another option would be the curse "Elemental Imbalance":
You wield an element’s might, but you are vulnerable to its opposite. Choose air, earth, fire, or water.
If you select X, you gain vulnerability to Y [opposite of X: fire-water, air-earth], cannot benefit from resistance or immunity to Y, and cannot cast spells with the Y descriptor. [shortened this one]
If you select fire, then this would explain why she can't cast water spells, but has to go via the Steam Caster route to cast some semblance of water magic.
I'm not a fan of this curse because of the huge drawbacks and the tiny benefits:
At 1st level, add burning hands (fire), grease (earth), hydraulic push (water), or shocking grasp (air) to your spells known.
At 5th level, add frigid touch (water), glitterdust (earth), levitate (air), or scorching ray (fire) to your spells known.
At 10th level, add ball lightning (air), calcific touch (earth), ice storm (water), or wall of fire (fire) to your spells known.
At 15th level, add chain lightning (air), contagious flame (fire), flesh to stone (earth), or freezing sphere (water) to your spells known.
So you get 4 spells of your element in exchange for an irremovable vulnerability to an element and dozens of spells eliminated from your spell list. I'd only consider it if you can get your GM to give you some tangible benefits for this curse.
Though - as is the rule for any curse with a huge drawback - it turns Oracle's Burden into a powerful debuff: remove all immunity & resistance to one element, and then add the vulnerability to it. Unfortunately, you can't make use of that debuff, because they're never vulnerable to YOUR element, but the opposite.
Max out UMD, take Pages of Spell Knowledge, and Rings of Revelation and/or the Soothsayer's Raiment. Since your build has little to no synergy, and seriously lacks in fire spells for a fire build, you'll need all the good items you can get. The "charisma for dexterity on AC and Reflex saves" revelation (Nature, Lore, Lunar) is a good start. The "Fiery Conduit" (Volcano) revelation lets you deliver your powerful oracle touch spells to those taking ongoing fire damage ("Burning Magic" revelation).
If you take the Coldblooded curse (and I really recommend it story-wise & effect-wise), you might even go for a rare counterspell strategy, since you can make better use of readied actions.