Nevaba is the imperfect past tense of the verb nevar, meaning "to snow". While "snow" is a common weather phenomenon, its use in the context of Madrid in summer makes it particularly striking.
In the song, Aitana sings, "Y en pleno verano Madrid se enfrió / Y mientras yo te esperaba / En mi corazón nevaba." This creates a powerful metaphor where her heart is experiencing a winter storm of sadness and coldness, even as the city of Madrid is in the middle of summer. It beautifully conveys the depth of her emotional pain and the contrast between her inner world and the external reality.
"24 Rosas" is Aitana's answer to an ex who wants her back after breaking her heart. She opens by rejecting the blame he put on her, reminding him that he was the one who left when things got hard.
Now he's calling, saying he loves her and wants to get back together, and he's sending roses to try to win her over. She calls it out for what it is: it's not fair, and it's not going to work. The gesture feels empty next to the way he actually treated her.
The chorus is her arguing with her own feelings as much as with him. She still cries thinking about it, but she keeps coming back to the same answer: no. The song is about choosing yourself over a relationship that already showed you it wasn't safe to return to, even when part of you still misses it.