i do want to be clear that from what i have read, it seems that everyone except Sin and Bollduilk (and maybe Azmira, i am not sure where she is) would had witnessed Ludios' "birth", for the simple reason that it was essentially akin to a volcanic eruption
even if they did not see her coming out of the ground, they would know something is going on
because the ground probably would had rumbled, or they might had seen ash fly up into the air and possibly even block out the sun in some places
Sin, Bolduilk and Azmira might not notice because they could be too far away
but everyone else is in the forest or mountains
which is probably close enough to notice