Is it that unusual?

OH sorry no one answered your post, I must have missed it, I don't have alot of experience with this I have been bitten but not enough to hurt like that, I don't think its abnormal I think it just depends on the bird and why its biting I found this article that might be useful for you.
http://pet-birds.pet-breeds.com/Biting_Cockatiels.html

Tiels seem to go along nicely then all of a sudden they have to have a mad five minutes and if your finger happens to be in the way, it gets bitten!!! Dooby does this occasionally, he always looks sorry after though, like he couldn't really control his beak. LOL. Yes, it does hurt, but I think females hurt a lot more apparently.

Plukie said:

Tiels seem to go along nicely then all of a sudden they have to have a mad five minutes and if your finger happens to be in the way, it gets bitten!!! Dooby does this occasionally, he always looks sorry after though, like he couldn't really control his beak. LOL. Yes, it does hurt, but I think females hurt a lot more apparently.

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I find females definetly different then the males, Ollie will full on attack out of the blue...hehe but he doesn't hurt, now Georgie she will hiss and open her beak but not bite me, she just gives the warning like she is big and bad

laurago said:

Georgie she will hiss and open her beak but not bite me, she just gives the warning like she is big and bad

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Sounds really familiar- move that finger the wrong way during a head scritch and you get an open winged warning with a hiss~ LOL- I stick my hand right in her beak just to prove her wrong and she then gives kisses! It's normal for tiels to do the fake bite and hiss thing BUT not to acctually cause injury.
AS far as with boys, I just got mine so I am not that familiar with their behavior but I do realize so far they acctually go for the kill. IF the bite is so severe to the point of actual injury I would suggest getting a pair of gardening gloves and trying again. THE ONLY THING that will stop a parrot from becoming a vicious biter is you ignoring the bite. It will eventually no longer associate him biting with you going away and will stop! I PROMISE. Whatever you do, do not move your hand away.

My female bluff bites frequently, if i scratch her head wrong, if i want her to step up off somewhere she wants to stay, etc but she has never bitten hard. Bailee, my male, bites hard when he's in a mood and he has drawn blood before. I've had worse though and i think my hands are building up a tolerance to bird beaks. I don't get too worried by bites because i can usually see what it is i've done to invite a bite.

yeah, I'm learning to let the bird know what I'm getting ready to do. I move a little slower, and make sure she sees my hand coming. She's getting used to certain things that I do, and is learning that none of them so far, are meant to hurt her. I've noticed that she only gets really mean when I do something different, or I startle her. She's getting better...but will still lunge at the cage bars if I get too close...I think this may be due to her age. I read that younger birds are a little mean when they're alone in their nests and anything other than mom or dad approaches. I've learned that it's all natural behavior up to this point, and should settle down in a few months...I just need to be patient.

Do you know how old she is?

I found out the other day that she's only 10 weeks old.