Golden rule: If the skin is bare or the fabric is skin-tight, people are allowed to look at it without judgement and you may not complain if you chose to wear the outfit. That goes for all members of the entire gender spectrum. Human species only though, your eyes start straying outside of that then you might be a little bit weird.
I think it's okay to look at them in cases like this, but don't just flat out stare for five minutes if she's trying to have conversation with you or something.
To be fair...
She is wearing the brightest thing in the frame.