Ross starts med school classes 3x each year (Sept, Jan, May). If she misses the registration deadline for the next term, she can always start the term after that. I guarantee Ross won’t won’t revoke her acceptance for delaying her decision.
Your D should wait at least until May-June before accepting Ross, and she needs to think hard about whether going offshore for med school is a good idea. She could easily end up with hundred of thousands of dollars in student loans, no job and no possibility of ever practicing medicine in the US.
Your D would be much better off if she would spend a year or two fixing the issues with her application (retake the MCAT, get US clinical volunteering, do US community service, acquire new or updated LORs) and reapply broadly to both MD and DO programs (or just DO programs depending on her MCAT score). Successful US med school applicants do not restrict their applications to a limited geographic area–like just New York state. Successful applicants apply widely usually to 20-25 med schools where their stats (GPA, MCAT) are in the middle 50 percentile of accepted students. She should buy access to the MSAR (Medical School Admission Requirements) for MD programs ($30) and the Osteopathic Medical College Information Book (free) for DO programs to see how she compares to typical accepted students.
It is extremely common. It’ sometimes called a “silent rejection”. Many med schools prefer not to send out final rejections until the end of application cycle–which is in May/June–just in case they need to interview more applicants to fill an unexpected shortfall in enrollment at the last minute.