Hi Lilly's Mum,
I have to say we had no problem stepping up...if anything Aidan seems to like Step 2 better.
As far as I knew the main difference is that Step 2 has more iron, though it depends on which brand you use. The reason I say this, is because we were looking at changing Aidan from Karicare to Heinz once he stepped up, however as Karicare Step 1 & 2 are both whey dominant & Heinz Step 2 is casien dominant (their Step 1 is whey dominant though) we decided to leave Aidan on Karicare as apparently the whey is easier for them to digest. Are you using Heinz? Could that be the problem?
Just a thought. I hope she's ok!!!