Where does T'Challas sister learn science from

In all due respect, your point is not the biggest problem with the Shuri character. After all, Asgard isn't real and neither is Sokovia. But we accept everything we see onscreen about them. The problem with the Shuri character is that they didn't devote anything to backstory or supposition to give some credibility to her being a genius in science and technology. Not unless you count dropping her into a hi-tech lab where everyone seemed to accept that she knew what she was doing. (Which unfortunately is even more than they did for the Disney SW Rey character).

Even a brief line or scene that covered her education would've helped. Then you add the comment from the actress who played the character, claiming she is even smarter than Tony Stark. And it seems to have gone viral with people who have seen the movie. You have to show some onscreen development to back up a claim like that. Add that all up and it makes her character come off as somewhat of a MarySue.