I left home at 18 to come to the other side of the world to pursue an education, with just $100 in my pocket. I knew nobody in a strange culture and a language I could hardly speak. It was tough and I worked both on campus and outside, including overnight shifts. But I survived and graduated with double majors in 3 years. I believe a well raised 18 year old can strive on her own not far from home and parents under the guidence of caring adults in a structured life with purpose.
eta. Aren't many 18 year old attending college away from home? These days, keeping in touch is so easy and free, which helps a lot for being away physically.
SF, I know you only from the forum, but even with that cursory knowledge, I'd never use you as a measuring stick for anyone else, even a champion skater. You're clearly an unusual person, with strong motivation, not to mention smarts to spare. You're fluent in at least three languages that I know of, and you work in a demanding job. And you say you completed a double major in three years....I know that Mirai must be an exceptional person, but I bet you beat her out in terms of drive and self-discipline. I'm just saying. I mean this in the nicest possible way, you realize. You just can't sell this particular argument as a rationale for Mirai.
(My mother was the daughter of an immigrant family, and she left home at just turned 16 to go off to college. The three older sisters were smart, but they attended a local college at home to save money. She won a scholarship and was seen off on the train. But she spoke the language, and times were more innocent then, I think. I don't assume that because she could do something like that, any old person could do it. Even her younger sister couldn't. That one, equally smart, went down to a distant college and was back home the next month. Got a law degree eventually, but couldn't hack it in her late teens. Not everyone can.)
I think an adult relative would have to go with Mirai, and i don't know whether the Nagasu family has an older sibling, cousin, or aunt to spare. When Michelle lived at Ice Castle, she was with her sister, and IIRC her father commuted a legendary distance by car every night to stay with the girls.