There's all sorts of mental defects from the mild and even funny, to the severe and life threatening. There's no telling offhand where she falls in the spectrum but the pecking is a good sign it's not too safe an area in terms of how it's expressed.
Keeping her and seeing how she goes will be very educational and depending how it goes you will know in future whether others acting the same are worth the while, or not.
Mentally normal chooks are 'kept in line' by imbalanced, vicious individuals, because they don't want to risk their lives, but mentally abnormal chooks won't be, they're generally incredibly short on commonsense, lol. Hard to guesstimate how she'll cope with bullies, she looks like the type to be high anxiety. That can further compel harmful behavioral traits.
As for the breed traits you were hoping for, well, her physical type is not up to breed standards, so it's reasonable to assume her other traits aren't either. All breed reviews are only applicable to a percentage of the breed, not the whole, not even the majority, because every breeder shapes the generations hatched under their stewardship according to their beliefs. Many believe extreme violence is acceptable among flocks and towards their human keepers, so they select breeders accordingly and it becomes a self fulfilling prophecy so to speak.
If she exhibits socially malignant traits like aggression, and they're inherited, then someone deviated from the standard ideal for the breed in order to produce her; if you breed her in turn, you're furthering this deviation from the temperament idealized as belonging to the breed. But many newbies don't know how important and influential the last few generations of progenitors are, and they expectantly buy a breed like it's a labeled food, expecting it to contain all the ingredients listed. Doesn't work that way; you have to 'vet' your breeders as carefully as you vet your birds, if not more so.
Hatchery bred sorts are generally crap examples of any breed. Even backyard breeders with some decent birds will still sell you crap examples of any given breed, quite often, simply because if they're selling it to you, they see faults they don't want to keep or breed.
If the bird was up to standard they wouldn't be selling it. If you want really decent birds, you need to generally be lucky enough to pick a breeder who is honest and ethical as well as generous, then answer the trick questions correctly ('what do you want them for?' --- if you answer that with 'just eggs, maybe some chicks sometime' then count on getting poor quality rejects)... And there's a host of other hoops to jump through too. Many breeders think what newbies don't know won't hurt them, the birds aren't destined for greatness anyway in the hands of a newbie. Not all breeders are like this of course, just plenty of them.
Best wishes with them all.