When my dd turned 1, we began adding just a half ounce of milk at a time to her Alimentum. We waited a full 2 weeks, then added another half ounce, waited 2 weeks, and so on. It took forever, but a quick switch just seemed wrong to me (although it is what the doc suggested).
I'm sure you've done this...but some insurance companies will cover the alimentum. If they have said no in the past, it might be worth trying it again, maybe your ped could get on the phone with them as well. I know it's a fortune...it was costing us $500 a month!!
If you do decide to try soy...read all you can about it...there has been some controversy.
Best of luck....she's going to outgrow it soon!!!!