As noted, it's difficult to answer the question completely w/o all of the relevant facts.
If your MOC uses competitive slates, you have shots at appointments off both of those slates. However, for the slate with your friend, IF your friend was slotted to the MOC, USNA won't know that he's turning down his appointment until he tells them. He has until May 1 to do so, but obviously could do it earlier. In the meantime, the other 9 go to the national pool.
If the MOC uses a ranked slate, USNA must (once they learn of the declination) offer the spot to the next qualified person on the slate.
So, you still have three shots. One is to get the appointment from the slate where your friend will turn down his appointment. Two is to get the appointment from the other slate. Three is to get an appointment from the national pool.
Whether your situation has appreciably changed since your friend decided to turn down his/her appointment depends on whether the MOC uses ranked slates and, if so, where you stand on each slate OR (for a compeitive slate) how USNA views your vis-a-vis the other qualified candidates on that slate. So, may be a huge help or no help at all.
And, yes, someone on the MOC's slate will receive an appointment, assuming there is someone fully qualified on each slate.