Daphne had finally understood what was happening― Nereus must have overheard her private conversation with Atticus and decided for some reason, he decided that he was going to help her win the contest! As such, Daphne understood his reasons for giving her the flowers.
Not only that, he was most likely also responsible for the sudden destruction of every other float and the sudden rainstorm. How else could she explain her float being miraculously untouched by the destruction that befell the rest?
Internally, Daphne was cursing herself for falling into the lake. This entire mess could have been avoided if she had not stood up on the boat.
"I knew it! You caused my float to go up in flames!" Fracessa seethed, her finger pointing at Nereus, who looked remarkably unfazed for a creature accused of arson, "I'll have you arrested!