I'm a pagan.
Had Christian upbringing since I remember, so would consider myself Christian most of my life, was a real firm believer for more than a few years as well. Was in my late 20s when I really starting poking on those believes critically and it just crumbled. I still believed there is something more. Weirdly, I didn't really deny the possible existence of Christian god - I just refused him.
I was in this weird limbo for years - not an antheist, not Christian, not really religious but believing there is something more on spiritual level but didn't do anything with it because I couldn't identify it. Kinda afraid of Hell, but also didn't want to suck it up and return to Christianity just out of fear (realized I had quite enough of it as a kid).
Then I randomly read something on modern paganism and something just clicked for me. Looked into it more and it just felt right.
CDproject always played with the lore a bit loose, so I'm sure the explanation will not be in line with book canon, but hopefuly it will be a good one.
My guess is some modified version of the Trials, less powerful but also less risky - maybe made possible due to her "herbal treatment" at Kaer Morhen. Or she just resumed the herbal treatment long term and these are the results.