If you ignore the ticket, the fine will double, collection costs and interest will be added, and they will get a judgement to garnish your wages or bank account. If that is, indeed, a photo of your wife's car with her face and the tag clearly visible -- and it was mailed to the correct address -- they can do this.
If she was not in that area on that day, or insists she was not speeding, ahe can take a day off from work to hang out with the drunks and druggies for a while so she can have her say in court. She does not need an attorney for this. If she shows up in court to dispute the ticket and it was not in a school zone, 50/50 chance it will be dismissed.
Bottom line: either pay it or fight it, but DO NOT ignore it thinking it will go away.
Oh, service through the mail is standard for Denver government agencies. A creditor or private party to a lawsuit needs to have it personally served with a notarized return of service filed, but the DA and traffic control can mail you a subpoena if they want . . . and if you fail to appear they WILL issue a bench warrant for contempt of court . . . even if it was mailed to the wrong address.
Denver does lots of illegal stuff on a fairly regular basis. That is just they way they do things here. It is effective, expedient, and they decide what rules need to be enforced.