we give advice about unemployment benefits, and not maternity leave benefits.
However, I can tell that for being able to get maternity leave benefits as unemployed, your wife must be entitled to unemployment benefits, meaning that she must have been member of a A-kasse for at least 1 year, have reported unemployed in the A-kasse and made herself available for work as a job-seeker in the job centre (or www.jobnet.dk).
This means that she must meet all the requirements for being eligible for unemployment benefits.
So, if a EU-citizen can receive unemployment benefits in Denmark, then the person can also get maternity leave benefits.
But as I read your question, your wife will not be able to meet the requirements.
Be aware that I only can tell you about the situation/right to maternity leave benefits as unemployed.
Anders Weber, www.a-kasser.dk