Tourbillon literally translates to "whirlwind" or "vortex". It's a vivid and somewhat dramatic word that isn't found in every pop song.
In the context of the song, Marwa Loud sings, "j'suis déjà prise dans l'tourbillon" (I'm already caught in the whirlwind). She uses it metaphorically to describe being swept up in the intense and perhaps overwhelming emotions of a relationship, making it a compelling word choice to entice learners.
Marwa Loud sings about wanting a relationship on her own terms: she wants everything, but she's also scared of getting hurt if her partner ever leaves.
The chorus, "Permets-moi de douter" ("allow me to doubt"), is her asking for space to be unsure rather than blindly trusting. She's done her own "investigation" and decided her partner is truly hers, but she's still wary after past disputes and nights spent sulking alone.
By the end, she pulls back: she doesn't want to be the one waiting around, so she chooses to stay independent ("j'suis mieux solo") rather than lose herself in a relationship she can't fully trust.