I realize this topic is very old, but want to offer some advice for anyone who might need it in the future:
Most universities in the USA have a health-insurance program for admitted students. For many, it's mandatory coverage, with an associated fee. They also may be able to steer a foreign student to one of their preferred private insurance providers. Your first move for health cover for a student coming to the USA should probably be to check the institution's website for guidance. Private health cover in the USA can be ridiculously expensive, and while the Uni's plan may not be cheap, it will probably cost much less than a private plan.
Because your daughter is a US citizen, she may run into requirements associated with the Affordable Care Act if she's in-country for an extended period of time. My experience is that quite a few of the Uni insurance programs meet the requirements.
Best wishes - N