according to the established cultivation lore that dieing, traveling and possessing should take at least a nascent soul level cultivatoin also she said herself ascend which is strange since she still has an internal alchemy which is the sign of golden core at the most
granted even if the words were chosen wrongly(ascend instead of advance) she could still have been at the breakthrough to nascent soul. but since she experienced tribulation she had to have destroyed her own internal alchemy at that point( surviving that and advancing is what triggers the tribulation)
yet after she wakes up she is 1she still has an internal alchemy albeit damaged and 2 is not surprised about it
to actualy fall from nascent to core is basicly impossible as the internal cultivation of the former is based upon the destruction of the internal alchemy of the later yes it can seem so outwardly but not inwardly