are you sure that the colored flecks you are seeing are not a little bit of the prevacid? usually it is purple, but it seems possible that watered down a bit could make it look like pink flecks instead of purple flecks.
i would think that if she was spitting up blood, that some of it would be passing in to her stool and showing up as occult blood.
i’m glad your doc is doing a scope, that should give you some answers. i would think that blood in spit-up would show up as pale pink or red, not dark pink.