(((Leslie))) A quick google does show that it's another name for IGF-1. But PLEASE... don't give up hope! My boy was diagnosed with acromegaly 3 YEARS AGO! And there is the stereotactic radiation surgery that Dr. Lunn is doing at Colorado State University (not sure if that's an option for you, but it's there). You already are getting some good control of Bayley's bgs and I see no reason that you won't continue to do that.
Of course this isn't a diagnosis that anyone wants, but it does allow you to know WHY she is "thirstier" for insulin than most diabetic cats. Knowing what's going on allows you to be PROACTIVE: make sure she gets good nutrition, keep an eye on her health via labwork, xrays, etc.
But you know what? You are totally right: Bayley is wonderful no matter what! She doesn't care what's "wrong" with her... she just knows that you love her and will take the absolute best care of her. And I know it doesn't seem possible, but the bond between the two of you will become even more special and even stronger.
So take some deep breathes, give your girl a kiss and a hug, and come back with whatever questions you may have-- no matter if they seem "silly."
((((((((((((((((((((hugs))))))))))))))))))))) to you and Bayley.