She said that she had an abortion in a clinic with protestors outside and that she was in college when she had her kid murdered.
In other words the oldest she could be is roughly 55 right now.
But most likely younger than 50.
She claims to be Catholic from a devout Catholic household. Catholic adoption agencies have never had racial exclusion policies (heck, one of my high school teachers years ago was himself an adopted biracial child and he was born in Pennsylvania in the 1930s and raised Catholic by a white family), and every "devout" Catholic can easily get in touch with a Catholic adoption agency.
She is a complete and utter liar and I challenge her and any of her supporters to document her absolutely preposterous claim.
Where does it say that the agency was Catholic? For all we know the agency told her that a biracial (black/white) baby would be impossible to place. Lots of states/agencies had policies back in the old days where black children (including half-black children) had to be placed with black parents. You said that your high school teacher was biracial, but not whether he was part black.
Of course, none of this excuses what she did. It was her own flesh and blood, she could have found a way to take care of the baby, even if she had to leave the child with the state.
Why do you think she was referring to a Catholic adoption agency? Nothing in the article suggests that. 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.