1) Then that group would have an extra expense on their hands, and I'm not sure why they'd pay for some girl to be a tagalong. Even if she was a good shot, wouldn't you trust a mercenary more than some street urchin?
2) See point 1.
There are numerous reasons a group like Red Jennys would have kids tagging along. Especially a group that sees itself as the sort to 'fight for the little guy' would have reason to help out, even if it's just to look good. Regardless it assumes alot that she would travel so far on her own without any help.
There are many people making the journey between the two capitols all the time. Indeed the biggest reason why capturing the keep in Crestwood is because it's right on the main road between the two cities. So it wouldn't be hard to assume that she could have made her way there the way so many other people do. She could have easily hitched a ride on a caravan as a stowaway.
6) Vivienne literally kills a marquis in front of an entire court of people just on your say so. Like I said, she is not the type to bluff.
OF COURSE Vivienne is the type to Bluff. Part of playing The Game is ALL about bluffing on a near constant basis. That doesn't mean she isn't willing or capable of backing up her bluffs, but she would have no problem making them in the first place. Scaring off Sera was definitely a bluff, though that does not mean that if she had to she would do everything in her power to back it up and actually try to find out what she can about Sera. Which would have been interesting to find out what she would learn.
8) Looking over the tidbit where she talks about it, I concede the point; she just says "I got caught stealing, you usually get alienage or worse for that, but then lady Emmald took me in." But that just makes everything weirder, because I'm pretty sure she's mentioned seeing the alienage tree, so she has to have been there or something.
One does not necessarily dictate the other. She uses "alienage" as a form of punishment but that is different then just living in an alienage. She could have been living in the alienage for a time and decided to leave because, to be honest, Alienages are ****-holes. She would then want to avoid getting caught and thrown back in there. That's what she was referring to. As for the nobles, yes the one in the City Elf origin was bad, but that's not a representation of ALL the nobles in Denerim.
Even then, keep in mind this particular noble took her in because she wanted a kid, it was for her own selfish reasons in many ways, even if she meant well in the long run.
9) ...Except she specifically says that she knew "some mages that were a little bit weird, but alright." Not sure what the argument is here.
Sounds to me that she gets that mages are people, but still doesn't like magic. So while she has no problem with the people who can do magic (so long as they're not using it to do bad things) she still isn't a fan of the magic itself.
10) In my playthrough of Dragon Age, I never once took her to Denerim. On top of that, if she comes with you in Hushed Whispers, its not like she recognizes King Alistair either (provided that you brought her along and made him King). If it really was at Denerim, then it had to have been an oversight on the writer's part, and why go through all that trouble linking two characters together unless it served some sort of purpose?
Alistair was never king throughout most of Origins, certainly not while you were walking around Denerim. It's only after the Landsmeet, and really after the final battle, that Alistair is made the true king. So it wouldn't be surprising that Sera had never met Alistair before; She barely remembers the Hero of Fereldan.