Hi Pangloss, your little girl sounds like a perfectly normal baby, thats what babies do, scream til they are red in their face.... when you see this as a 'personality problem' then you are not seeing it as a baby doing what babies do. Some babies are more 'settled' than others. My three all different but turned out fine (well youngest is still young, but going good). Some kids are more emotionally charged than others. My eldest daugher was a big screamer, had to carry her around on my hip for years, lol.
Son was less vocal.... but carried him around anyway, lol, had the habit by then, they have both matured into well balanced young adults. I saw them as being individuals, not cookie cutter babies.
A baby can't tell you their skin feels like it has ants crawling all over it (ie, has allergies etc) or if they are more sensitive to sounds, lights etc.
With children, if they are problematic, I see it as "how do I update/improve my parenting skills to support this child's temperament".
Don't see your little girl as someone who may 'emotionally maul you', she is just a little girl, be supportive of her and do some Supernanny type child boundary setting.
I'd go for nurture more than nature.... the behavioural problems are handed down through the generations.
Check out my blog on this site and the other one thats linked (fareastofwest).
I've written stuff that works. Simply reword and rephrase the way you communicate.
Melody Beatties Codependent No More to read would be my suggestion and Supernanny on DVD/books.
Good luck