This is something I just sort of thought of . I've read a lot of stories where she has gone on to have children, and i guess that's what I'm getting at, do you really think it is possible for her to have kids?
I personally, and saddly I might add, don't think this is possible because she may be alive but she still feeds on blood , there is too much vampire in her for that to happen and also when she becomes an adult she will stop growing and changing- just like all the other female vampires in the family meaning it won't happen.
My other thought, warning scientific thoughts ahead, is that also werewolves (shapeshifters) are sworn enemies of vampires. I can only imagine that is similar to trying to breed a lion and a wildebeast. There is no way she and Jacob could be genetically compatible enough for a baby to excist. I know, however, that the most obvious issue would be venom- which is deadly to werewolves. On the upside Nessie has none- she bites her future mate all the time.
I like the idea that some people dream about the pair creating a new super specias. In fact in one of my fanfiction stories I've almost done just that. I don't think Nessie and Jacob will ever have childen for those reasons.
If anyone thinks they can prove me wrong then please do, I want to see if there really is an obvious answer to this question, since it was never really put into place by Stephenie Meyer in Breaking Dawn or in the official guide. What does everyone else feel about this