Bella, as a human, has always been somewhat untouchable by most vampire's powers. Edward cannot read her mind, Jane cannot torture her, etc. Anything that has to do with manipulating or tapping into the mind does not work on Bella. As a vampire, this "power" remains, and she is untouchable. She also has great powers of restraint, and whereas most "newborns" would go crazy at the scent of a human, Bella is able to restrain by running away from the scent, and eventually easily rejecting the urge to drink blood of humans.
Bella can create a shield around herself that can make sure no one can hear her thoughts but on top of that she can expand it to shield her loved ones as well.
Bella's power is basically begin a shield from mental attacks such as the numb and fire mental attacks the twins from the Voltaire have. She has the ability to contract the shield from herself and spread it across a vast group of people. In the ending when the Voltaire is starting to attack silently Bella sort of helps saves the day by blocking everyone the mental harm that the Voltaire twins try and inflict.
she is a shield.
like when she was human her mind is protected but she can push it away from her to be able to protect other peoples minds like hers she can also take it away from her self where edward can read her mind and other people can use their powers on her
Sorry, I'm having issues. Here's my full response...
Bella doesn't actually have powers in Twilight, but in Breaking Dawn, as a newborn vampire, she is a shield. This means she is able to guard herself from mental attacks, but not physical attacks. Throughout the story you see that she learns to extend the shield to protect those around her, and eventually, she is able to lift the shield from her mind so Edward can read her thoughts.
she's a shield