I think for all Elizabeth's ideology-first attitude, she has come to realize the more human dimension of living in the USA and that includes letting a kid believe what he thinks is the truth rather than just wrecking his life further what with the whole evil-empire thing going on at the time.

I definitely buy her changing - and I even think there are plenty of reasons why younger Elizabeth might have immediately offered to do something so very, very, very against the rules, despite being a believer. But not mentioning that at all seemed bizarre!