This DM would rule that a fire lash is very much a whip
The level 1 pyrokineticist psi-like ability fire lash says
A pyrokineticist gains the ability to fashion a 15-foot-long whip of fire from unstable ectoplasm as a move-equivalent action. She takes no damage from a fire lash she creates, and if she releases her hold, it immediately dissipates. The lash deals 1d8 points of fire damage to a target within 15 feet on a successful ranged touch attack. A pyro can take Weapon Focus and Weapon Specialization (if she otherwise meets the prerequisites) in conjunction with the fire lash, as well as any feats that apply to the use of a standard whip. The whip remains in existence as long as the pyrokineticist holds it. (Expanded Psionics Handbook 152)
(Emphasis mine.) Considering that the game allows weapons to be created from water and ice (e.g. the special materials riverine (Stormwrack 128) and blue ice (Frostburn 80), respectively), having a weapon that functions as a normal whip even though it's made of "fire from unstable ectoplasm" (whatever that means!) doesn't seem—to this reader, anyway—particularly unusual. Added to that is the idea that the pyrokineticist can apply any of her feats that affect a whip to the fire lash effect, this DM would have no problem with the fire lash effect being in all respects treated as a normal whip except in its origin and except as the psi-like ability fire lash describes.
To review, the traditional whip (Player's Handbook 117, 122–3) (1 gp; 2 lbs.) is a one-handed exotic reach weapon that, when designed for a Medium creature, deals 1d3 points of nonlethal slashing damage. In addition, the whip's longer description says
A whip deals nonlethal damage. It deals no damage to any creature with an armor bonus of +1 or higher or a natural armor bonus of +3 or higher. The whip is treated as a melee weapon with 15-foot reach, though you don’t threaten the area into which you can make an attack. In addition, unlike most other weapons with reach, you can use it against foes anywhere within your reach (including adjacent foes).
Using a whip provokes an attack of opportunity, just as if you had used a ranged weapon.
Because a whip can wrap around an enemy’s leg or other limb, you can make trip attacks with a it. If you are tripped during your own trip attempt, you can drop the whip to avoid being tripped.
When using a whip, you get a +2 bonus on opposed attack rolls made to disarm an opponent (including the roll to keep from being disarmed if the attack fails).
You can use the Weapon Finesse feat… to apply your Dexterity modifier instead of your Strength modifier to attack rolls with a whip sized for you, even though it isn’t a light weapon for you. (122–3)
Thus this DM would rule that the fire lash effect functions exactly as described above plus…
- If the pyrokineticist loses her grip on the fire lash effect, the effect dissipates.
- The pyrokineticist can take an attack to make a ranged touch attack (and all the baggage that comes with that) at a foe within 15 ft. Success means that the foe is dealt 1d8 points of fire damage.
That second point should be discussed with your DM. It's unclear if the fire lash effect's ranged touch attack can be substituted for an attack or if using the fire lash effect to make a ranged touch attack takes a unique standard action. (This DM would totally allow the fire lash effect's ranged touch attack to substitute for a traditional attack—allowing, for example, iterative attacks—if for no other reason than the pyrokineticist's player is playing a pyrokineticist!)
Because it's otherwise a whip, this DM would also rule that the fire lash effect can be the subject of the pyrokineticist's psi-like abilities weapon afire and greater weapon afire, especially seeing as how these are the only ways the traditional high-level pyrokineticist can make the fire lash effect a worthwhile weapon (relatively speaking, anyway).
Bear in mind that besides feats like Weapon Focus that mandate picking a weapon, very few feats specifically reference the whip, but this DM would allow, for example, a fire lash effect to be used to realize the benefit of the truly awful feat Vae School (Drow of the Underdark 57), and absolutely this DM would allow the fire lash effect to be used in conjunction with the skill trick Whip Climber (Complete Scoundrel 90).
Unlike the similar prestige class master of chains (Sword and Fist 27–8), the prestige class lasher (25–7) is not by this document officially superseded by the prestige class exotic weapon master (Complete Warrior 30–1), so this DM would likewise allow the fire lash effect to be used with any lasher class features that also necessitate using a whip.