Were Gabrielle privy to Ginny's inner doubts, she would have agreed without hesitation that Ginny was right to question whether or not Gabrielle was sincere in her interest. Beauxbatons girls refined flirting into an art, and Gabrielle's heritage meant she had no shortage of partners to practice her skills on. Gabrielle would have furthermore explained that she would be flirting even were she completely uninterested in sleeping with Ginny, because Ginny was pretty and because Ginny would flirt back.
With events as they were, however, Gabrielle did not know of Ginny's doubts, and so instead of explaining, she merely smiled at Ginny's eagerness, and waited patiently for the older girl to finish her goodbyes.
Gabrielle followed Ginny to the fireplace, only considering for the briefest of moments where they should spend the night. "The Delacour Chateau would be appropriate, I think. Maman and Papa are asleep at this hour, but I have a fireplace of my own, and-" Gabrielle's eyes raked down Ginny's body before she continued, "My room is Silenced. They will never hear a word we say." Or any names you may scream.
"Shall we?" Gabrielle took a handful of Floo powder, declaring, "Gabrielle's room in the Delacour Chateau," and stepping into the flames.