She saw no point to it, so she didn't participate. And maybe that made her a bad person, a terrible friend, but she swore not to sacrifice her happiness for the depression of someone else. That's not fair.
Where's the sense in it, anyway?
She buzzed around, laughing and talking, ignored them when they glowered at her. It didn't stop her from crying at night in silence, but at least it cheered them for a couple of minutes each day.
It was all she could ask for.