I think there are so many factors that helped her out. She had time to prepare, her shield, she always wanted to be a good vampire, she hated the smell of blood as a human...so I think that helped her from not hunting that hicker the first time out. I also think that renesme helped out out one way or another, she had a child and wanted to be a good mom.
I also think that if she acted like a "newborn" then the story wouldn't of been such a hit!
well it seems she was predestined to be a vampire, then add to the fact that she started drinking blood while pregnant then she didnt have the frenzied thirst that comes from being a newborn. she was already use to it therefore was able to control it better.
i say its because she hated the smell of blood when she was human so it came with her to the vampire life,even though she doesn't hate it as a vampire its just that it doesnt appeal to her as much as it should
:D as Edward said: her mind is funktions backwards :D she just wanted it to be with him just nometter what will happend. as a person was she very strong to put her wishes on the last place and think on others.. it´s really imasing how hard person she is, i wish i could have a half of her strongest :( of course it could be becourse of her shield too...
I think Bella handled itso well because for one, she had a very long time to prepare herself, and for another i think maybe because Nessie was half human so she thought oh well if i dont do this right then i willl kill my daughter, so i think she did it for Nessie, & because she had time to prepare, like she had time to think this over think of what she was supposeively going to be like and Bella never wanted to be that crazied new born plus she is a shield so maybe her sheild is part of it! that is somethingu should ask stephanie meyer!
I think what helped her was a few things compiled together. She knew what to expect, she was ready for the transformation, and she learned from the Cullens. Plus her pregnancy with Renesmee, she had to drink blood for the baby because she couldn't keep anything down. It seems as though she was destined to be a vampire because of the way she handled the transformation.