I was thinking about this yesterday and while I love everything about Babe's character (except her accent that can sometimes sound very put on at times), but apart from her accent there has always been something that doesn't quite fit.
I think it's her relationships with the members of the Carter clan. The fact that she is Sylvie's sister is all too much and hard to believe. Had she been the Heather to Sylvie's Shirley and just more of a friend to the family as opposed to an actual member her existence would be easier to swallow. - in my opinion.