She can understand Mandarin, but can’t read or write.
I don’t know about colleges, but the fact she understands Mandarin is a very valuable skill. I would encourage her to take Chinese and go to a college with a good Chinese language program—sounds like for her it is mainly learning the characters, which I know is very tough and boring and takes a lot of rote memorization, but for an American to know Chinese is golden in terms of getting a job in international business, finance, etc., or anything else to do with Asia, since China has become so important and yet so few Americans can master the language. Your daughter is already halfway there and she should learn to read and write now while she can, she won’t regret it.
I’ve been around people who speak Japanese most of my life, including my wife and her family, so I understand a lot of that language, but I know it’s too late for me to really know it because even if I learned the hiragana and katakana alphabets, I am too old to memorize the kanji. Not enough brain cells left. That kind of makes me sad. I have been taking Korean for a while; there the problem is the opposite. They use a phonetic alphabet which is easy to learn and extremely logical, but the spoken language is difficult, to me much more difficult than Japanese because linguistically it is harder to speak and it also retains the different levels of formality of speech much more than in Japanese.
Anyway, just my two cents on your daughter mastering Chinese.