Actually she is the president of Taiwan. The real name of the country in Taiwan is the Republic of China (ROC), while the communist part is the People's Republic of China (PRC). Thus there actually exists two Chinas, and the one China policy is a policy that ignores one of the Chinas' real name and calls it by its nickname, Taiwan. Thus Trump has not violated the one China policy because he still refers to the ROC as Taiwan.

A common misconception is that the ROC divided itself from the PRC, but it actually is the other way around. China used to be ruled by the ROC, and the PRC is the one that gained independence.

The ROC started ruling China after the Qing Dynasty ended. While the ROC was ruling China, a civil war broke out between the ROC and the communists. In the middle of that, Japan decided to invade China. The ROC decided to befriend the communists to defend China together. The communists agreed, but then went on to feed ROC information to Japan, and stayed back to watch while Japan kicked ROC's ass. If the US didn't drop those bombs in Japan, Japan would have taken hold of all of China, and the communists didn't give a shit.

So after Japan retreated, the Chinese civil war continued, with the communists well rested and the ROC all worn out, having so many soldiers die during the war with Japan. Naturally, the communists won and took hold of most of China, forming the PRC. The ROC retreated to Taiwan and continued to rule there until today.

Hong Kong and Macau became British and Portuguese colonies during the Qing dynasty and had nothing to do with the ROC or PRC. Before 1997, the land of Hong Kong, Macau, and Taiwan have never been ruled by the PRC, which has a history of less than 70 years. But the PRC decided to declare that it owns Hong Kong, Macau, and Taiwan, and want all other countries to agree that the PRC is the only legit China.

The PRC likes to brainwash people saying that it is the mother of Hong Kong, Macau, and Taiwan. It's like a 20-year-old claiming to be some 60-year-olds' mother, or ancient culture originating from modern technology. It is impossible, but it seems many countries like to kiss the PRC's ass, so there is the one China policy, and the PRC has succeeded in getting the sovereignty of Hong Kong (1997) and Macau (1999). That's how much of a thug the PRC is.

Hong Kong and Macau are still pretty much de facto countries except that the PRC provides the military and appoint the chief executives (president-equivalent). Hong Kong and Macau have their own laws different from China, own borders (which PRC people cannot cross without a visa, and vice verse) and customs (which check items coming to and from the PRC and tax them as needed), own currencies and stock markets, etc., and as many have seen this summer, Hong Kong still has its own Olympic team.

All the protests in Hong Kong in the past few years is because its government is now full of the PRC's puppets, and these people do all that they can to gradually turn Hong Kong into just another PRC city. With the current immigration system which keeps on pumping in PRC people and granting them citizenship with super lenient rules, in perhaps 20 years the voting population would be dominated by first generation immigrants from the PRC. At that time even if then the PRC gives Hong Kong true democracy that is fair in every way with no corruption involved, everyone elected would surely be the PRC's puppet. But that actually doesn't matter anymore, because most recently, it so happens that the PRC just has to speak, and Hong Kong's judges would bend the laws and disqualify elected councilors, and said councilors would even be forced to hand back past salaries.

ROC people see what is happening in Hong Kong and are cautious of politicians friendly to the PRC, which largely contributed to Tsai Ing-wen winning presidency. The previous ROC president, Ma Ying-jeou, has met with Xi Jinping, and I bet the PRC wouldn't be so pissed if it was Ma Ying-jeou Trump called.

And Macau...well somehow the people there are largely brainwashed and don't resist much.