It sounds as though you were one of the earliest of early adopters, and that the process of getting photographs from phone to phone was elaborate if not impossible at the time. Also, while New Zealand may have been ahead of the game, it seems that the US (where one of the girls involved was living) and the UK (where the other girl was sending an image from) didn't have camera phones until 2002.
UK/Euope:
US
I think it is highly unlikely that one of them texted the other a photograph. Given that fact, if this is an argument that is going to be used in a court case, they should be really careful that they have their facts straight. If they mess it up, they could lose the case if Prince Andrew has a lawyer who can undermine the credibility of the witness.
This is more likely, but again, it is really important for them to avoid making and repeating claims that might end up sounding incredible.
Regarding the famous photograph that Prince Andrew disputes is real. Does anyone know if that could have been a digital photograph or would it have to have been on film for that level of resolution? Could it be a scanned picture? Or one that came out of a digital camera?