DCL will not allow you to change your cruise if you booked through a
travel agent, you have to call the travel agent and they will make the change for you. Your deposit is fully refundable up to at least 3 months before the cruise (refund period is different depending on what category room you booked). But you are way ahead of any of the time constraints. I have two suggestions:
1. Cancel the cruise you booked through the travel agent and the deposit will be refunded. Then call DCL and book the new cruise and put down another deposit. Only problem with is is you may have to pay another $600 on your CC before the original deposit is refunded, depending on your billing cycle.
2. When you call your travel agent to change to the other cruise, ask them for a room that has at least one adjacent room available. If they are a good travel agent they would be happy to do this for you. Then have your friend call her travel agent, change the cruise and request that adjacent room. I've never tried this but it should work.
Also, once you both have your reservations, one of you should call to have your dining linked together. You will need both reservation numbers, then call your travel agent and tell them you want to dine together.
Have a great time!!!