I am a sponsor for a candidate for confirmation with RCIA. My candidate has a former husband who is a Protestant and is refusing to go through the annulment process. Does this mean that she cannot obtain an annulment?

No. Either party can petition for an annulment. Canon 1510 specifically provides for a respondent who refuses to accept a legitimately served citation, and Canon 1592 §1 allows the judge (tribunal) “to declare the respondent absent from the trial and decree that the case is to proceed to the definitive sentence and its execution.” You might ask the candidate to pick up a copy of Edward N. Peters’ book, Annulments and the Catholic Church: Straight Answers to Tough Questions.