I suspect for the story direction the dev is pursuing, they made sasha too powerful. So, she had to be removed somehow since she was a clear asset in our corner that could wreck chaos if she desired.
She was powerful from the beginning, the thing is, Gretel was behind all that, she needed a body and Sasha shared the body along with 2 other glows... in this case Gretel and Melanie, so basically she just took advantage of the situation (Johan vs Sasha) and got the body
