It's safe to say she's not in there yet as I opened about 400 of the darn things during the contest and didn't get one. Dozens of Err witch, Wolf and Bulwark though.
I'm slightly suspicious about Void wyvern being in gold chests also. I'm sure a few have had him out of it, but since it got released I must have opened 250-400 gold chests and I still haven't pulled that Toon, I've had the same ones many many times but Void is still locked in my list.
Murphys law dictates I'll get it the day after I finally farm the 80th stone to unlock him. Which will be 2020 seen as he's only available in two chapters and sometimes they yield 0 stones in all 6 fights.