What she means:
In Dreamworks Dragons: Race to the Edge, season 4, episode episode 2, "Gruff Around The Edges", Hiccup refers to Tuffnut as "one of my best friends." Which means that not only does he consider Toothless his best friend, he considers the rest of the gang his best friends. Hiccup has multiple best friends and that is so wonderful.
that scene in httyd where toothless draws on the ground with a log and hiccup has to dance around the lines and there’s this really beautiful and spirited music playing and it ends with hiccup in front of toothless and he’s holding out his hand and looking away and toothless touches his snout to hiccup’s hand like. that scene always gets me and idk why but it’s honestly one of the most memorable and fucking beautiful moments in cinematic history.