PCP may be out of date - check with other staff / team leader / communication with professionals folder for up-to-date info. Offer the service user an alternative meal, checking that any alternatives are in keeping with individual's dietary requirements. Refusal to eat one meal may just be due to lack of hunger, but if accompanied by other symptoms, arrange doctor's appointment as lack of appetite could be linked to tummy bug or other illness.
Conflict is basically between support worker wanting to ensure a healthy lifestyle for the individual, and to ensure that the individual is not hungry or thirsty. But at the same time, must take into account the service user's personal choices - people have the right to change their mind as often as they like, and so personal care plans must be constantly reviewed and updated. A refusal to eat for non-medical reasons should be referred to the team leader - has the individual been certified as an adult with incapacity? If so, this should be referred to someone in the medical profession for further investigation.
Hope there's something there of some use to you! ;) xxx