First of all, thank you all for your great replies. I really do appreciate them!
My Sophia: Thank you soooooo much for the tips! Great advice. I will take it all to heart. It will go in my compiled research file for flying (which my mum will have to read every single bit of, ha!). I need to wait to buy a harness because pups grow and I want an accurate measurement close to when we're picking her up.
RDB911: The bags are darling! I hope to get one in the future, but they aren't what I'm looking for right this second. I want to let my pup get to full weight/dimensions before I invest in such a lovely (but expensive) bag lol. That way, she'll be comfy and maybe I can even get the smaller size!
Dianab28: A care kit for the pup will be packed! We've come up with a solution to the bag dilemma (see below). We took the smaller carrier advice to heart.
keokis mom: That's what I thought about the Kwigy Bo bags. They look absolutely darling, but don't seem like what I need right now.

For day to day use though, they get a stylish A+ ^_^ Thank you for the recommendation on the Sherpa!
To all:
I ended up purchasing the Sturdibag (see link below). It was on sale and became cheaper than the Sherpa. Plus I liked the padding inside, the ventilation, the flexibility, the zipper locks, and especially the seat belt track for car rides! It is also pretty snazzy looking in red!

It will also fit Rylie even if she goes above the 12lbs mark at any point. If she doesn't end up getting that big, well she'll just have more room in her carrier!
SturdiBag Bordeaux Pet Carrier at PETCO
I called the airline we plan on flying with (after checking their policies online) and discussed the Sturdibag with them and they said it would be fine. We have a back up plan in place just in case the people on the phone were lying to me :P (they often do that). My mom's friend has an airline approved carrier that is within dimensions that we can borrow just for the trip home (and being a itty bitty baby still Rylie will have no problems fitting).
So crisis averted! Yay! I'll let you know how we, Rylie included, like the Sturdibag. It got rave reviews in general from what I've seen though. I'm pretty excited!!! Is it lame to be excited about a dog carrier? :P
NOTE: Numbers 3 through 6 on my original post are still open to answers/opinions/tips, so please feel free to respond to them! Thanks!