Ze giechelde om de haverklap om de flauwe mopjes van haar vriend.

She constantly giggled about the lame jokes of her friend.

giechelen – to giggle
om de haverklap (ieder ogenblik) – every other minute, continually, constantly
flauw – 1. bland, tasteless 2. silly 3. weak 4. lame
de mop – joke
om – points to an object of an action