Ik

She will need to accept that admission first so as to be a bona fide student of that school before taking any further steps.
Beside I hope she had at least a credit in biology because biology is one of the prerequisites subject in psychology! After successfully completed her admission, she can opt-in for transfer from agric department to psychology department but I doubt If this can be process within a short period of time, I mean it usually take forever in some school.
Best of luck to her.