Wu Zhao (624?-705) – to give her the name that she herself wished to be known by – was the only woman in the history of China to rule in her own name. This, in itself, was sufficient to ensure that her name has been blackened since her death by generations of Chinese, since female rule was considered an outrage to the natural order. Official histories, and, later, less formal writings on her and her reign combine to convey the impression of a ruthless, selfish, sexually wanton woman – and they do so precisely because these are characteristics that best damned Wu in the eyes of posterity, and acted to ensure that no other empress could ever rule the country. So, no – what you are encountering online is not material sourced in reliable accounts that date to Wu's reign; rather, it is calumny designed (consciously or not) to denigrate the very idea that a woman should hold political power, or that an empress could be considered in any sense a competent ruler.

I should probably pause before going on to observe that, because the vast majority of the detail that we possess for Wu's reign dates to the period after her death, it is extraordinarily difficult to recover anything of the real woman behind the various legends that are told of her. We can, I think, conclude that Wu was not only intelligent and highly competent, but also self-willed and significantly ruthless – nobody who lacked such qualities could possibly have risen, as she did, from the position of fifth-rank palace concubine to become the consort of a reigning emperor, much less seize power for herself. But it is certainly very arguable that she was no more violent, or more ruthless, than some of the men acclaimed among the greatest of all emperors of China. On the other hand, while both dynastic histories and a later rather ripe vein of erotica, written during the Ming and Qing dynasties and alluding to the empress as a sort of metaphor for unbridled female lust, combine to give us the impression of a woman who remained – disgracefully – sexually active into her eighties, I think we can be pretty confident that nothing remotely resembling the scenario you set out ever actually occurred.

There are enough of these stories, admittedly, for Wu's most recent scholarly biographer, N. Harry Rothschild, to devote an entire chapter of his book on the empress to addressing the topic of "Wu Zhao as lover." Rothschild explains that male writers felt it imperative to portray Wu as a woman "in thrall to her senses" in order to put her down, and thus "restore her to her proper station" – one of subservience. In these stories, her body is described as flawless, like jade, even in old age, and her appetites as "incandescent... excelling the nymphomaniacs and most lustful prostitutes of the day." But this Wu, it can be argued, was written to call to mind a well-known Daoist immortal, the Plain Girl, who was said to lure and seduce lonely peasant men in her lakeside hut. "Through her consummate skill in the boudoir arts," the Plain Girl "goaded men to extremes of passion" – and, in doing so, was able to absorb "all of their spent male essence." This was significant not merely because the immortal left her lovers "withered, enervated husks," but because she also robbed them of the Daoist ideal of masculine self-control. In this reading, the perfect skin that Wu boasted into advanced old age was not some genetic gift, or even a literary metaphor: it was clear evidence she was a sorceress capable of rejuvenating herself by draining the maleness from her younger lovers.

All this was extremely unbecoming in a ruler. As Rothschild points out,

a man, particularly an emperor... needed to carefully regulate his emissions and avoid frequent ejaculation. Otherwise, he would lose his male yang energy and become both sexually depleted and, without [that] to sustain him, politically emasculated and thus less effective in the public, administrative, arena.

The unbridled Wu, then, in this reading, was displaying her unfitness to rule in every sexual act, and if one reads the official histories of her reign in date order, it becomes quite clear that the writers are drawing a parallel between Wu's ascendant political power – which she has deliberately drained from the men who ought to possess it – and her moral and sexual descent. The sort of woman who, as a concubine, could ruin the emperor Gaozong by encouraging him to submit to his most shameless appetites, and "contort herself into a wide range of gymnastic positions to cater to the Emperor's peculiar tastes," became a ruler whose inadequacy was made all too apparent by her willingness to openly take numerous young lovers from the peasant class – including, in many of the most widely-retold myths about her, Xue Aocao, a man renowned for possessing the largest "meaty instrument" in the whole of China.

Read this way, stories of the type that you have encountered online perhaps make greater sense. Wu was a woman who took things that she should never have had, using explicitly female arts, and an explicitly female body, to undermine and then seize for herself what should have been explicitly male power. And (while I rather doubt the story you have cited is contemporary) this could certainly extend to whatever power male envoys – and the foreign powers they represented - brought to court. As the contemporary poet Liu Binwang put it, she used her sexual glamour to destroy the men who surrounded her:

”All fell before her moth brows. She whispered slander from behind her sleeves, and swayed her master with vixen flirting.”

Sources

Mike Dash, "The Demonization of Empress Wu," Smithsonian 10 August 2012

Dora Shu-Fang Dien, Empress Wu Zetian in Fiction and in History: Female Defiance in Confucian China (2003)

N. Harry Rothschild, Wu Zhao: China's Only Woman Emperor (2005)