Desencontrar is a fascinating word that literally means "to un-meet" or "to miss each other." It's formed by adding the negative prefix "des-" to "encontrar" (to meet).
In the song, the lyric "Sexta-feira é dia de desencontrar" (Friday is a day to miss each other) suggests a playful or perhaps fated sense of near-misses or paths not crossing, setting up the eventual meeting as something special. It's a unique way to express the idea of not meeting someone.
Ana Gabriela's "Se É Pra Você Ficar" is such a sweet song about finding someone special when you least expect it and being willing to change everything for them. She meets someone late at night, on a Friday, which she says is usually a day for people to unmeet ("Sexta-feira é dia de desencontrar"), but this person totally won her over. She says, "Me apaixonei não posso te deixar passar" [I fell in love, I can't let you pass by].
It's all about that feeling when you know someone is worth making big changes for. She sings, "Mudo tudo de lugar / Se é pra você ficar" [I change everything around / If it's for you to stay]. It's like she's saying, "I'll rearrange my whole life if it means you'll be in it!" She even talks about wanting to run to them and show them how much she's changed, admitting she might have said things before that hurt them, but now she's ready to go "mais além" [further]. It's a really heartfelt declaration of love and commitment.