I beleive both you and her. I just don't think it would be nearly as terrifying to most people in 1938.
Then again, I am wrong quite often, as my mom reminds me! ;-)
Protestant here...but the roots reach back into Catholicism. Imagine the rain filled skies to split "as predicted" and witness the sun hurtling closer towards the earth...enough to dry the ground and peoples drenched clothes... I'd be terrified and felt that I had just witnessed what God's wrath was capable of. Not a "doubting Thomas" here! A long productive life for Sister Lucia as she rejoins her cousins in their heavenly reward.