Rebecca is a pretty name. I like
Becca and Bex the best as NN's. I'm not too big on
Reba though.
Rebecca Eve and
Rebecca Annabel are both pretty, although I think that
Rebecca Eve has a better flow.
I prefer the sound of
Rebecca, but
Pamela is also nice. I think that it would be fine to use it without a NN. I actually prefer it without a NN. I knew a
Pamela who always went by
Pamela. No one (at least not to my knowledge) called her
Pam. I agree that
Pamela Laurel is a bit too heavy on the L's.
Pamela Ruby flows very nicely though.