Well, did some quick research on Nina Paxton and her Philco radio. Looks like it may have been a Model 38-9K. If so, an impressive piece of furniture but not much going on inside. No RF stage and only one IF stage. No spider web style antenna inside but did have provisions for an external antenna. Looks like frequency coverage was standard AM BCB and shortwave from 5.7 to 18.2 mcs. So, reception would have to have been on the 6210 freq ( or maybe the second harmonic???). IMHO, would have been a real fluke of nature given her location, time of day, and equipment at both ends to have heard anything.
Anyway, why didn't Earhart or her navigator use CW? They would have had a far better chance of being heard.