I really hope that that's what happened to Sky.
But I just don't understand why she would hand off Sky (whom she never really had a bond with) and not M, who was clearly favored more.
She may well have thought that would hurt Soloman more than M disappearing. I believe her main, no -SOLE motivation, was wretched meaness toward Soloman. Nothing more complicated. Certainly not 'protective', nah. Lacks the capacity.
Since she may have never bonded naturally with Sky, it probably was easy for her.
I kinda hope she suffers horrendously watching M being deliriously happy with Soloman while she sinks into the depths of hell.