when you do a transfer from one A-kasse to another you are member in the new A-kasse from the day you have applied. How much time the A-kasse use to process the transfer is not relevant for you.
So you must register as graduate/change status to graduate in the new A-kasse at latest 14 days after graduation.
If you already have access to the new A-kasse's online self-service solution you should change to graduate status there. If you don't have online access to the new A-kasse yet, I will recommend you to write/call your new A-kasse and tell them that you want to be registered with graduate-status.
Anders Weber, www.a-kasser.dk