Literal

Maysilee 🤝 Haymitch

Mckenna Grace got top billing on the IMDB page for SOTR (which is a little shaky because there's still 500 days to release but still)

Every book has had a "songbird", Orignal trilogy had Katniss, Ballad had Lucy Gray , and Sunrise would have had Lenore Dove, who does sing and is also covey. However we don't see her sing on page (Haymitch says it makes her nervous and he's reaped before we ever see her sing)

We do however see Maysilee sing, infront of Haymitch in fact. Also of all the younger castings revealed till now, Mckenna Grace is the most well known and also an established singer which could prompt Lionsgate to give her a bigger role.

Which would be enabled by her being the "Songbird", and will also be a nice parallel to her being the orignal Mockingjay pin owner. They could be doing a bait and switch by mentioning Lenore Dove by revealing covey status but making Maysilee the singer (twist on Lucy Gray's role in Ballad) just to suprise book readers.

She also has the Lucy Gray recall when she says her Grandmother refrenced her saying, so that could be expanded by Lionsgate too.