It doesn't. However, a self-described "devout" Catholic's default setting in such a situation would be to seek out a Catholic agency - and a Catholic agency would never have rejected the child on any grounds.
For all we know the agency told her that a biracial (black/white) baby would be impossible to place.
She says they rejected the child outright - not that they said it would be a difficult placement. And given the time frame, they would have been blatantly violating federal law.
You said that your high school teacher was biracial, but not whether he was part black.
He's half black, half Polish.
Which moots Government Shrinker's point about poor Robin being stuck in a college town with no car. If she visited the David Duke adoption agency and they told her to get lost, fine, but clearly she either avoided the Catholic alternative or she is lying. Or both.