I got into an argument with a guy that says that the hair of a White-Haired Witch, despite the text saying ' This functions as a primary natural attack with a reach of 5 feet. ', that her hair is not a natural weapon, and that I could not use with iterative attacks as a natural secondary weapon (what the Natural Attacks rule says). He claims that the phrase 'fonctions as' doesn't mean that the hair is a natural weapon.
Treat it as a natural weapon in every instance and it will remove the need to do mental gymnastics. This means no iterative attacks.
Your hair counts as a natural weapon except where the rules specifically states your hair doesn't count as a natural weapon. Nitpicking "functions as" changes nothing unless the rules actually identify times it won't "function as" a natural weapon or lists some caveat. And the rules do not.
I believe it's possible to still have the iterative attacks when using natural weapons.
Natural Attacks
Attacks made with natural weapons, such as claws and bites, are melee attacks that can be made against any creature within your reach (usually 5 feet). These attacks are made using your full attack bonus and deal an amount of damage that depends on their type (plus your Strength modifier, as normal). You do not receive additional natural attacks for a high base attack bonus. Instead, you receive additional attack rolls for multiple limb and body parts capable of making the attack (as noted by the race or ability that grants the attacks). If you possess only one natural attack (such as a bite—two claw attacks do not qualify), you add 1–1/2 times your Strength bonus on damage rolls made with that attack.
Once again, the white-haired witch natural attack is subject to all rules regarding natural attacks except where it is specifically stated not to be. Ergo, unless you have some text which lays out that they are to be treated as a manufactured weapon for the purposes of iterative attacks, or you took the Feral Combat Training feat with a level of monk, or got some other exception, you would be stuck to only taking a single hair attack per attack action (full or otherwise).
Except it never state it is a natural weapon in the description, it say "gains the ability to use her hair as a weapon. This functions as a primary natural attack with a reach of 5 feet." I understand how it can be confusing but it's stated it function as a primary natural attack, not a natural attack or a natural weapon, hence it can't be used in as a secondary attack. Believing it's a natural weapon is interpretation. In every other descriptions of abilities giving natural attack it's always implied that it can be used either way, look for metallic wings, lesser fiend totam, even the claw of the draconic bloodline specify it function as a natural weapon, not a attack.
From the definition of natural attacks:
Creatures with natural attacks and attacks made with weapons can use both as part of a full attack action (although often a creature must forgo one natural attack for each weapon clutched in that limb, be it a claw, tentacle, or slam). Such creatures attack with their weapons normally but treat all of their available natural attacks as secondary attacks during that attack, regardless of the attack’s original type.
Your hair doesn't need to be a secondary natural attack by default to use it with weapons - using it with a weapon makes it into one. By your reading of the rules, humanoid creatures with bite attacks could never make both bite and weapon attacks in the same round, because the rules specify that bite attacks are primary attacks (without giving any special clauses for being secondary attacks). As can be demonstrated through the SRD entry for werewolf, this is most definitely not the case.
Primary natural attacks become secondary when used in conjunction with weapons. The hair doesn't need additional text specifying this because it is a general rule.