It's possible that Melinda deduced the fact that the interview would air.
Interesting. However, very, very rarely does Nancy Grace air an interview between her and another subject pre-recorded.
Greta is the same. If you see Greta interviewing someone and it's not live it's likely:
1) An interview out of the country (Aruba, for example, while covering Natalee Holloway).
OR
2) An interview with a well-known politician or former President.
(In my best Red Skelton Klem Kladiddlehopper voice) "Noooooooooo. Think so?"