After a couple of mins, I told them politely "hey looks like your headphones are not connected?".
She then goes "Oh, I know. I'm not using headphones".
I then said "can you reduce the volume please? it is too loud".
She then goes "Oh it is not that loud I'm sure".
I then go once again "Can you reduce the volume please, this is a public transport and some passengers are trying to read or rest".
She then goes "It is not that loud" and then proceeds to reduce the volume only slightly.
I give up and go back to looking out the window.