If my co-defendant was sentenced to prison and her part of restitution was placed on me to pay, can I get an attorney to write an order contesting it?

If you are the co-defendant in the action you are writing about and do not have legal counsel representing you with respect to the issue raised in your question, I recommend that you get an attorney to contest the amount of restitution of the co-defendant placed upon you to pay resulting from the criminal matter you have been charged with.

Sentiment is that you cannot be obligated for a part of some one else's restitution order unless you have an opportunity to be heard on the subject.