She claims to have come from a "devout Catholic" household. In practicing Catholic households, one automatically seeks out a Catholic adoption agency - no supposedly Catholic family would seek out a secular agency first. Unless she's lying about her background, her first impulse would have been to seek out a Catholic agency which would have welcomed all children regardless of ancestry.
If she was in college, in a white area, and didn't have a car (and few coelge students did in those days), and obviously didn't have access to the Internet, she probably had access to only one or two agencies, and had no real way of finding out whether policies were likely to differ at different agencies.
Every devout Catholic would know that any Catholic agency would have an "all children are welcome" policy.
First, she was away at college, and the implication is that her family wasn't aware of this, so there was no "Catholic family" seeking out an adoption agency. Furthermore, in the past, Catholic adoption agencies had (and maybe still do) a strict policy of only placing children in Catholic homes, and of race-matching (which was the norm for all agencies until fairly recently). Many non-white babies turned over to Catholic adoption agencies ended up in Catholic orphanages, and not being adopted into families. Until the advent of the large-scale welfare state, in which most adoption and foster care of "hard to place" children began to be handled by government, or government-funded agencies, most adoption agencies were either highly sectarian outfits, or for-profit (though on paper they were no doubt "non-profits"). There is no profit whatsoever in placing non-white babies in the U.S., and never has been. And sectarian agencies are limited by the racial make-up of their membership, and would have been even more strictly limited a few decades ago, when nearly all adopting parents insisted on a child who would look like their biological child, and didn't plan to tell the child s/he was adopted.