It's not possible to x-ray through padded clothing like bikinis. Anything you've seen on the contrary was either a fake, or it was a bikini you could already see through in the first place.
And in this instance, no, her bikini is not see through even though her nipples are poking through. They're distending the fabric from underneath, that is not the same thing as the cloth being see through. An x-ray effect won't show anything you can't already see.