All ATF contracts regardless of rate guarantee immediate advancement to
E2 (not E3) after graduation, I was always told that it was measured from when your orders are stamped to go to A school (which would happen the same day). She will not wear any rank for the graduation ceremony because she isn't eligible yet.
She will receive E4 after graduation from A school provided she has the TIR, has completed POSLC and is within standards on her PRTs.
People who do not have ATF may not know how it works, even if they've been in the Navy for a while. If you want all of the details, read the
instruction.