I don't get why people are mad about the girl, it's not like she's lying to people to hurt them or manipulate them, nor she would talk bad about people behind their back I'm guessing. She's like Teruhashi from Saiki Kusuo no sai nan, she's actually very pretty, has good grades and good athletic abilities, she's basically perfect, but she can't go around saying the truth (or else she'd probably be hurting people then, and I'm betting she needs to lie her way out of difficult situations from creeps and other people bothering her, the kind of unwanted attention an attractif person gets), and she feels like saying nice things to people/encourraging them especially those like this guy who seemed really down and left out.
If a little white lie or two helps a friendless boy to feel a bit better isn't that fine? Again it's not like she's doing it mock him.
Anyway, it's interesting how this concretely shows how those who are popular/physically attractive in our societies's standards have to pull up a façade, while those who aren't can afford to be honest since they have nothing to loose. And how lies can often be a mean to protect others (like the girl) or ourselves (like the boy did) and not just to hurt, but how in a way it's all pretty sad.