Definitely invest in another convertible seat to keep her rear facing. Although I am much more concerned about the laws of physics than the legalities of car seat use, I agree that Illinois has the law that children must be properly restrained but doesn't state how. That said, there is not a child restraint out there that says that a child under the age of 1 can be forward facing. Many seats also have minimum height requirements too. I believe any seat made by Dorel (parent company for Eddie Bauer, Cosco, and Safety First) has a minimum height requirement of 34 inches before the child can forward face. The seats may be just fine for a forward facing child that is shorter than that. However, the company states that this was the min height at which their seats were crash tested. So basically using it with a smaller child is potentially making that child a crash test dummy - something that no parent would knowingly do, though sadly, many indavertently skip over that requirement.
Also, car seats expire. Most are good for 6 years from the date they are manufactured. This has to do with the breakdown of plastics due stresses from not only use, but simply exposure to changing temperatures - freezing winters and blistering summer days. Think how hot/cold it gets in your car/garage. Also, safety regulations change and improvements are made so it is best to not buy a seat until you really need it. I made this mistake more than once before I found out about this. I think I would try to sell the seat on Craigslist and use the money toward another one that can rearface her for a while more.
As for placing her in the center, that is a whole other issue. While it is technically the safest, that is not true if the seat doesn't fit there well. Also, there is a school of thought that the least protected child should go in the most protected seat (ie the middle). The least protected passenger is the one without a car seat, followed by the booster, followed by the harnessed forward facing, and most safe being rear facing. But, when you have multiple carseats (we have 3 in a dh's Focus)sometimes making them all fit dictates where they go.
And I can only just shake my head at the people who claim their kids will be fine as long as they drive carefully. All it takes is one distracted or drunk driver and your life could be changed forever. It is on the news all the time. I wonder if they ever ask themselves how they would feel if the unthinkable happened and they knew that they could have done more to prevent it.
I didn't learn about the importance of rearfacing until my 2nd child was over 2. I actually turned her seat back around (she was within all the rear facing requirements) and she could have cared less. She rode comfortably and safely that way until shortly before her third birthday. My 3rd child rode rearfacing until after 2. My 16 month old rides rear facing too. He has never known anything different. And even though he throws a tantrum sometimes, I won't compromise on this. And I know enough from experience that the tantrum has more to do with being restrained than being a certain direction. I tried flipping the other kids forward facing to curtail. It worked temporarily but before long they were just as mad about being strapped in their seats forward facing. They all grew out of the seat tantrums eventually, some taking longer than others. I know I have already written a ton, but I think these pictures are very interesting. They are comparisons of how a child's spine develops and really shows why rear facing is safest. http://www.windsorpeak.com/vbulletin/showthread.php?t=180970