Unfortunately, she might be.
The holy trinity (WFT, Marth, Villager) only got two months in production, and look how fast they got rare.
Rosalina has only had one month in production. Normally, I'd say that's not TOO bad because in the US, only Target is getting her, meaning loads of stock should be available (since Target normally stock high on exclusive toys), but with that maniac trying to buy all of the Rosalina Amiibos he can, on top of the sheer, genuine demand for her, thinks are looking rough for Rosalina's Amiibo. She might even end up worse than Little Mac at this rate.
EDIT: Visualisation of what I said above: