The answer to your question is rooted in the historiography of China during this period. Before responding to it, however, I should note one slip in the question itself: Wu was the consort of two Chinese rulers, Taizong and, subsequently, Gaozong. Ruizong, on the other hand, was one of her sons by Taizong, whom she installed as a puppet after her first husband's death.

If we rephrase your question to apply to Taizong, however, the straightforward answer is that we have no reliable sources whatsoever to answer it. There are, in fact, two multi-volume official state histories of the Tang dynasty, the Old and the New Books of Tang, both of which cover Wu's life and reign in some detail; both, however, were compiled centuries after her death (in c.945 and c.1050 respectively), and hence also long after Wu herself was denounced as a usurper. The consequence of this, in historiographical terms, are very considerable, since it means that the entirety of the material we have on Wu was written from a specific, hostile, standpoint which sought to portray her as a dangerous and unworthy ruler. It has been seriously proposed, in consequence, that we can effectively know nothing about this period of Tang history at all; and even if we do not go to such extremes, it is certainly the case that the information contained in these histories about Wu's rise is very likely to be seriously distorted, and written to portray her in the most scheming and least flattering possible light.

With all that said, however, you may like to know what the two Tang histories do say about Wu and her relationships with Taizong and Gaozong in this period. The information is still extremely limited, but I summarised it in an essay on Wu's treatment in Chinese historiography for the Smithsonian a few years ago. This is still available from my history site, and I extract from that:

... Matters are complicated by the fact that little is known of Wu’s earliest years. She was the daughter of a minor general called Duke Ding of Ying, and came to the palace as a concubine in about 636 – an honor that suggests that she was considered beautiful, since, as Jonathan Clements remarks, “admission to the ranks of palace concubines was equivalent to winning a beauty contest of the most gorgeous women in the medieval world.” But mere beauty was not sufficient to elevate the poorly connected teenage Wu past the fifth rank of palace women, a menial position whose duties were those of a maid, not a temptress.

The odds that a girl of this low rank would ever come to an emperor’s attention were slim. True, Taizong – an old warrior-ruler so conscientious that he had official documents pasted onto his bedroom walls so that he would have something to work on if he woke in the night – had lost his empress shortly before Wu entered the palace. But 28 other consorts still stood between her and the throne.

Though Wu was unusually well-read and self-willed for a mere concubine, she had only one real advantage over her higher-ranked rivals: her duties included changing the imperial sheets, which potentially gave her bedroom access to Taizong. Even if she took full advantage, however, she must have possessed not only looks but remarkable intelligence and determination to emerge, as she did two decades later, as empress.

Attaining that position first required Wu to engineer her escape from a nunnery after Taizong’s death–the concubines of all deceased emperors customarily had their heads shaved and were immured in convents for the rest of their lives, since it would have been an insult to the dead ruler had any other man sullied them–and to return to the palace under Gaozong’s protection before entrancing the new emperor, removing empress Wang and the Pure Concubine, promoting members of her own family to positions of power, and eventually establishing herself as fully her husband’s equal. By 666, the annals state, Wu was permitted to make offerings to the gods beside Gaozong and even to sit in audience with him–behind a screen, admittedly, but on a throne that was equal in elevation to his own... One critic, the poet Luo Binwang, portrayed Wu as little short of an enchantress–”All fell before her moth brows. She whispered slander from behind her sleeves, and swayed her master with vixen flirting”– and insisted that she was the arch manipulator of an unprecedented series of scandals that, over two reigns and many years, cleared her path to the throne.

That, pretty much, is it, unfortunately. So I'm afraid that the answer to your query is that we simply cannot know. I'd add that the historiographical background is so unhelpful that any further speculation is likely to be useless to the point of being actively misleading. Sorry.

Source

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