What does blah mean from a girl?

Excuse me, could you please clarify what the term 'blah' might signify when used by a girl in conversation? I've noticed it being used in various contexts, but I'm unsure if it carries a specific meaning or if it's simply a filler word. Is it meant to convey boredom, disinterest, or something else entirely? I'd appreciate any insight you might have on this matter.