This is the part of Half-Blood Prince. Hermione cried after seeing Ron and Lavender kissing together in a celebration. Hermione then casted the spell oppugno which if I'm not mistaken, it made the birds aggressive.
There's a background music playing when Harry saw Hermione crying on the stairs. The music intensified when Hermione asked Harry if he loves Ginny.
It's a solemn and sad music. It's just instrumental and I don't know what's the title of the music.