As far as I can tell つぶやく is invariably translated as 'to mutter/murmur' in bilingual dictionaries, and yet hardly ever do I see it used in a context where I feel this translation seems appropriate.
This maybe isn't the best example but it's the one that inspired me to ask. Two girls have just run into a shop to escape from a dog:
"That was a close call"
muttered Maruko breathing heavily.
To me mutter/murmur is something you do under you breath, probably to yourself. It doesn't seem to fit here.
So I'm wondering what Japanese speakers think of when they hear the word つぶやく, not just in this sentence but also more generally.