Britney Spears' younger sister Jamie Lynn performed a little showcase at 3rd and Lindsley Bar & Grill yesterday (June 14) in Nashville, and the girl sure has grown up since her 'Zoey 101' days.

"I'm so happy to have all of  y'all here, thank y'all for coming out tonight," said the 21-year-old mom to her audience. "This next song is called 'I Look Up to You,' and you can imagine who I wrote it about, so I hope y'all like it a lot."

It doesn't take a rocket scientist to figure out that Jamie Lynn wrote the song about her older sister, our Queen, Britney Spears. The siblings, who have always been close, shared a lot of ups and downs over the past couple of years -- including Brit's infamous breakdown and Jamie Lynn's teenage pregnancy -- so it's charming to see how much she looks up to her big sis.

"Scared little girl living on a big old world / You've outgrown your room / It all happened way too soon," sings a pensive Jamie Lynn in a country twang. "They took away your innocence / But we've still got a strong defense / If I didn't get sieved in this / I'd be lonely."

Jamie Lynn shows promise as a pop-country star. She's a true southerner whose past is filled with enough heartache to pen a few more songs (she plans to release a country album). Also, it's kind of nice to know she's trying to make it on her own and in a different genre than her sister.

We're still eagerly waiting on Britney's response to the song, though.

Watch Jamie Lynn Spears Perform 'I Look Up To You'