Quite a few photos to give any real critique on, if you picked maybe 1 or 2 we could critique a little more specifically however,
Those all look very good for a first shoot! Working with a model, whoever it is can be tricky the first few times. Personally my favorite is #9650 because of the "natural expression". I think that is one of only a couple where she doesn't look "posed". I don't mean to sound like I'm giving you a hard time for that hehe, its still something I'm working on as well, trust me. Directing a model is tough, and just takes practice and a LOT of time examining photos from pros, that's me at least, I try to have a least a few shots pre-visualized before I shoot, so I can direct them to do exactly what I want, and evoke confidence; remember you are the director. I think to make these photos really stand out some even basic post processing is really required, that will bring them up to where they belong. Technically speaking most look very good to me, just a tad bit underexposed for skin tones overall, but I would correct that in post processing; better to do it then than lose data. Also, really watch your focus, I spotted a couple that were very out of focus, and then a few that were a tad soft, which is "okay" if its going on Facebook or something, but if you want them to look great, focus has to be spot on; tack sharp, no exceptions. Unless of course you are getting creative, however thats a whole different story
Good colors though, and your sister looks great in these, very good first shoot, keep shooting, can't wait to see more! Oh and, if you want to see more portrait work, check out modelmayhem, this site is good, but that one is specifically for fashion and portraits if that's more what you want to see. Best of luck