I think it's wrong that my wife wants me to do all of her online course work. I won't do it.
Why does your wife want you to do all of her online course work?
Because she doesn't understand most of it and she needs the degree for her job.
Your wife's job expects her to learn and understand the material she's studying. If you do her work for her, she'll never learn it and she won't succeed at work. Help around the house so she has more time to do her own coursework.
I've tried to tell her that but she won't listen.
Talk to your wife and tell her that you'll help her to learn the material but you won't do it for her anymore. She needs to do the work herself so that she learns and understands it.