In Twilight, when James bites Bella, if Edward let her change, would she have the same power that she has in Breaking Dawn?

yes, the reason is that in her human form she already had the ability to block certain people. For example in her human form she was able to block Edward, Aro and Jane... dont know if i am missing anyone else.

Good question! But, yes she would have the same power. The vampire that changes a person does not influence the power they get at all.

Well, yeah!!!!!!!!!!!!!!!!! of corse she would they would just mot have renesmee/nessie!

YESS

yes