So, when Sansa Stark jumped, fully intending to die alongside her brother and reunite with her family, the ritual lost its delicate balance and exploded. The magical vortex expanded and started sucking in the ancient ice magic weaved into the Wall, further amplifying and unbalancing the ritual. The strength of the flame would have turned her into ash in seconds if she wasn't related by blood to Jon Snow and if not for the ancient magic from the Wall pouring into her body and protecting her from the ritualistic fire. Harry's soul was also pulled from the abyss by the strength of the magical vortex. A being who had been one step short of godhood in terms of magical prowess.