>>75610646DESU this is probably the closest to reality, if a bit exaggerated
It's highly unlikely that Cover holds any actual animosity towards Doki (especially after all the shit that's happened to her and the waves of support she has in the west), I doubt any of the talents and her have bad blood (unless of course Enna and Millie spread BS to Kiara during their trip, but that's speculation and I can't say if she'd even believe it), and we know that she's still on friendly terms with Moomer and a few Stars.
Regardless of what the unicorns say, the existence of Holostars is pretty inoffensive to the greater Hololive brand
Since we all but know for certain that Mooms and Donkler want to collab at some point, it's not hard to believe that Cover/Yagoo/the managers elected to allow some of the stars to participate in this with her to test the waters and gage reactions (from Holo fans, Dragoons, the western Vtubing market, sisters, Niji itself, etc...) to see if letting her collab with the main company (ie. Mumei)
Do I know for sure? Hell no! But it's a decent explanation
One thing's for certain, this effectively kills the 'She's publicly blacklisted' rrat dead, or at least a hard blacklist and something more along the lines of "she's involved with a bit of controversy with our main rival (putting it lightly) and it might stir shit if one of you collab with her publicly. Do it in your past life if you really want to" sort of thing. Clearly that's changed though