Basically agreeing with numerous posts here --
I don't see that Disney would care if you shared portions, sampled each others food, etc.
An issue would arise if the OP was trying to use her credits to buy a meal for the non-
DDP friends. However I did not get that impression that was what was planned.
For example if a guest KttW card reads 2 adults 1 child, but 4 adults and a child were at the table, the server is not going to allow 4 adults and 1 child to use the DDP credits at one meal, one ticket.
There have been an occasional post about someone stating they were charged an entertainment fee if some in the party were not dining, using credits or sharing a meal. (Such as LTT, which will soon be character-free anyway.)
I don't see any issue with using snack credits in addition to a meal credit at a counter service. Heck, who would want to restand in line after eating their main meal just to use a snack credit or two?