According to the mainstream history, Himmler called off the gassings in late 1944 as the Red Army was approaching Auschwitz, and ordered Jews to be given better care, as part of an attempt to cover up the exterminations. (As part of the cover up, he also ordered the four working gas chambers demolished, which is why they are in ruins today, though the mortar of the demolished buildings still contains considerable traces of hydrogen cyanide, something the deniers cannot explain.)
So Anne Frank being taken care of in a hospital in early 1945 is completely consistent with the mainstream history.
Other Jews were treated in the Auschwitz hospital before the exterminations ceased. But this is also consistent with the mainstream history. The desperate Nazis wanted to economically exploit the Jews before killing them, so if an able bodied Jew could be brought back up to snuff, they would not kill him, and would even treat him. Your problem is explaining why the Jews treated in the hospitals were teenagers or adults, not (until Himmler ordered an end to gassings in late 1944) very old or very young people.
With a handful of exceptions, very young people (children, not teens like 15 year old Anne Frank) simply did not survive Auschwitz. The meme photos you have seen of liberated children are either non-Jews, Jewish twins who had been preserved as guinea pigs for crackpot medical experiments, or Jews who arrived in late 1944 after Himmler's order to stop the gassings.
Deportations from one camp to another are also completely irrelevant and well understood by mainstream historians. The problem you have is explaining how millions of Jews disappeared in the Nazi camp system during the war, deportations from one camp to another do not explain this.