Ok, here's the deal: she's not opaline.
Which leaves several options:
1. The father is not actually opaline
2. The father is split for opaline
3. There's an issue with the way the mutation is expressed (i.e another mutation that cancels the effect of the opaline mutation or a further mutation which prevents expression of the gene at all)
4. There was a reversion of the opaline mutation back to wild type
Ok: the father is definitely opaline, so that knocks out 1. I don't believe there's any recorded evidence that opaline does anything when it's only present on one X chromosome, so that knocks out 2 because theoretically it's impossible for him to show phenotypically opaline if he only had 1 copy.
That leaves 3 and 4. It's impossible to tell which one of the two it is (unless you sequence her DNA but that's... let's not go there
) and they're both extremely rare. However, it's not impossible, so this is most likely the reason she's not opaline. I guess that's good news because you aren't going crazy, she really isn't opaline
Also, this is all assuming that she's the only female that's not opaline, which means that all other chicks MUST be male. If for some reason you get another female, we're going to have to look again at potential issues with the father's mutation as the likelihood that two of these mutation/reversions happened in the same clutch is so close to nothing it's considered to be impossible.