My basic line of thought on this is that, first, superhero comics only wound up dominating the American comics market in the real world due to the Comics Code Authority making it impossible for the lion's share of their competition in the market space to get their material published, and second, that a world where superheroes were real would change up the economic and social dynamics enough to make it unlikely that something like the Comics Code Authority would come into being. There probably was still a moral panic of some sort, but it would be less focused around comic books, and probably more focused around things like superhero registration acts, or something along those lines. Or at least, that's what I was thinking.
As for the comics Ace was in, she would have stuck around Earth in her series, but that's mostly due to the overall plotlines that both hers and Captain Paragon's series had. Basically, Captain Paragon originally took up that name because he was a Captain in the military on his homeworld of Venus. Home to an oppressive, isolationist regime, Venus was ready to start up an expansionist phase by conquering their nearest habitable neighbor in the solar system, Earth, and they treated the Captain with a special super soldier infusion that gave him his ability to absorb and transmogrify radiation. When he arrived on Earth, he found that he gained additional super-powers once freed of the oppressive atmosphere on Venus, and after getting a taste of good old American Freedom, he decided to start falsifying his reports to try and dissuade Venusian High Command from invading and make a new life for himself on Earth as a Paragon of justice.
Ace herself first appeared in the multi-part story 'The Trial of Captain Paragon', where it was revealed that she was the Captain's favorite cousin, living back on Venus, whom he had been sending letters detailing the truth about what he was up to on Earth. Ace's wicked stepmother found some of those letters while snooping around her room one day, and quickly turned them in to Venusian High Command, which lead to an exciting conclusion to the first act of the story when the Venusian Military Police arrived on Earth and used their own Venusian super-powers and advanced alien technology to apprehend him. He was dragged back to Venus and put on trial for high treason, and after a fantastical trial in which Ace herself pretended to betray her cousin by operating as chief witness for the prosecution so that she could learn the details of what they were planning and help to foil them, the Captain was eventually stripped of his rank and dishonorably discharged, but given the punishment of permanent exile to Earth, rather than the death sentence that High Command had originally been planning. Also, she managed to get them to seriously postpone their invasion plans, too.
Ace herself initially made the decision to stay back on Venus in order to help inspire the Venusian people to reform their government, but reader response to her was strong enough that she made a reappearance a few issues later, having been given the same radiation infusion as her cousin and then smuggled to Earth by the newly-formed Venusian Resistance. She's been his partner ever since, though the writers of the main line of Captain Paragon Comics mostly used her as a device to help ramp up the odds against the Captain himself, having her get captured or hypnotized, or turned into a colossal lumbering fish monster so that the Captain could further prove his heroism by making some clever use of his powers to save the day. Especially after she became popular enough to get her own solo title, since then she had her own book where they could put the adventures that were more focused around showing her worth as a hero while keeping the main book all about the Captain himself.
So Captain Paragon and his sidekick, Ace the Wonder-Girl, were more specifically written as defenders of the Earth than anything else, and while Ace has a lot of knowledge about alien civilizations due to having been raised in one, she doesn't actually have much experience exploring them.