If you are written up or warned for this, and then there is another occurrence, another complaint, it may very well lead to your termination, without recourse of any kind, including unemployment insurance. I am sure your situation with this resident is very frustrating, but what you said was inappropriate. If you continue to talk to people in a disrespectful and inappropriate manner, you may be fired. No one is saying you should love changing the lady, but it is a situation that is part of your ordinary work load. And it is totally inappropriate for you to say anything negative to her while you are providing the care.
In this case it sounds as though you actually may have been a whole lot more forceful and disrespectful than a polite "I can't keep changing you." Face it, you were out of line. If you move on and don't repeat the offense, they probably will not terminate you. It's hard to find people willing to work in these very stressful and underpaid and unpleasant jobs. But that doesn't mean you can take it out on the residents.