Yes, she is a junior.
So, you think Santa Cruz would accept with those stats despite a D?
The problem with retaking is that she would have to start at the community college 2 weeks before the school year is over. So, if her grade turns out to be C-, she would not know it yet.
Seems like a waste of time.
On the other hand, are you sure, that retaking it replaces the grade completely, and not just averages it out? Do you still need to report the D on the UC application along with the make up grade?