Odds are – that’s why she’s wearing headphones in the first place. Because she wants to be left alone.
Especially in this day & age of freedom for all genders – this advice is good for women, men, and transgendered, equally.
It also has no bearing on the reason for your approach. Whether it’s for sexual flirtation, or if you want to ask the time of day.
One attractive woman I know wore headphones on her daily bus commute; sometimes even if the batteries were dead. All because she didn’t want to be approached. Mind you, this is a classy lady, and if someone genuinely needed assistance, she’d be there immediately.
But just like many people – sometimes she just wants her own quiet time to herself. A little downtime where she’s not required to interact.
When someone’s wearing headphones (or reading) – it’s a clear signal they want their privacy. Don’t Interrupt!