Sarah Palin as VP would bring in women independents and fence sitters that maybe wouldn't vote or would vote for Hillary. Also, some women who are lukewarm on Trump would vote for both because Sarah Palin is VP. It may make the difference in swing states.
Also, an unknown factor is how many Latino women would prefer Sarah Palin over Hillary Clinton? I suspect a lot. Most Latinos, especially the women, are family oriented and religious.