I think she thinks she's punishing us by refusing to take her meds, or eat dinner. Any ideas for someone who is over the drama?

I don't have enough information on your situation - is she at your home- or in AL - has she had a recent change in her life - i.e. loss of spouse, move, medical change?
Is this a new behaviour - have her meals changed - if so in what way -
Meds? - If you could provide more information - 
It may seem like she is being an obstinate person - but this disease unfortunately causes these behaviours - hard to see past them - as they can be so hard - don't take it personally!!! 

Is she losing weight? If not, ignore what she does or doesn't eat. Does she eat other meals or snacks, but just not dinner? Don't try to figure out motives. She may or may not be trying to punish you. What Ahmijoy says about eating when she is hungry certainly applies to healthy people. Unfortunately some folks with dementia have impaired hunger sensors. Don't surround the eating issue with any drama. "I'll put this plate in the fridge for you, MIL. I'll warm it up for you later if you want it then." No more discussion.

As for not taking her pills, what medications does she take? What are the consequences of not taking them regularly? Can you remove the drama from this, too? She refuses her pills. Nod, put them away and wish her goodnight. If it continues report it to her doctor. You cannot force anyone to take medications. Drama isn't going any good, right? Drop the drama.

My fairly with it Mom often refuses to eat,, at almost 90 LBS she says she is fat.. OUr Dr told us to ignore it.. its is an attention ploy with her ( My aunt agrees and she is with us often) we have found if mom says she is too full to eat dinner.. and we just let it go,, she often has "just a bite" before bed.. or if we just take her a plate while she watching TV she will eat it. Her weight is stable so I know they are right!

My mom always said “You catch more flies with honey than with vinegar.” You may have to treat Mom like a child when it’s time for her meds. Promise her a reward if she takes her meds. As far as refusing to eat, shrug your shoulders, leave the food in front of her for, say, half and hour and then remove it. Make sure she’s not sneaking food when you’re not looking, and she will eat when she’s hungry enough.