Used mostly in casual conversation among friends or peers, not in formal situations. Karaoke is not her scene, so she declined the invitation to the party.
Pro Tip 2/3
Personal Preference
It expresses a personal dislike or disinterest in an activity, place, or social setting. He said nightclubs aren't his scene because he prefers quiet evenings.
Pro Tip 3/3
Subtle Disdain
Can imply a mild disdain or disapproval for the activity or environment being discussed. Opera isn't my scene; I find it too long and pompous.