You can see she yells at him for not taking things too seriously, but she is really worried about his safety at the same time. She even comedically stretches his cheeks as she scolds him for his obliviousness. Here we don’t see any reaction from Sabo Luffy, as he is the dense male, but we can understand that these two share a great relationship, even if it’s just being good friends. She is the hot headed female who is the “care-taker” of a male character and comedically refutes wanting to do that but in reality she would stand by him till the very end no matter what happens.
Next, is she is shown to be very emotional and crying towards the potentialreaction that Sabo Luffy could have gotten from losing Ace. She was worried and even cried for him, showcasing a bond that transcends traditional familiarity. Not even Hack Zoro was shown crying from almost losing his leader. While it’s definitely obvious he did feel worried, Oda decided to keep the only comrade to cry for Sabo Luffy as Koala Nami.