You'd think she would have joined the Coast Guard.
Sorry for missing your earlier note, Rev. Henrickson.
I don't know the answer. I know nothing about Coast Guard requirements, but I'm guessing her age was the issue, plus maybe location.
Historically the Army has been more willing to waive age requirements than any of the other services since the Army has a greater need for more people, and also because the Navy and Air Force have been reducing their personnel for some time, including periods when the Army was expanding. For a while the Army had a formal program to process people through AIT who had left the Navy and Air Force but wanted to re-enlist in the Army. I don't know why this woman had to go through basic and couldn't do that AIT program — maybe the program doesn't exist anymore, or perhaps she had been out of uniform long enough that the powers-which-be decided she had to go through basic to make sure she could do the job.