K Thompson--
yes, thats right, they must file either where you live now, or where the debt originated. I would first check to see if the summons is for a valid lawsuit--the court clerk's office where they claimed to have filed this case can verify that for you.
I am a bit confused about your post--you said they got a judgment against you according to the letter, but now this is a summons to appear in court? is that right? Something's not quite right there. First, if they got a judgment against you and you didnt even know about it until that letter came, then they broke the law right there. you can try to have that judgment vacated, you will need to file an order to show cause where that judgment occurred, and request that the court vacate the judgment due to improper service. the fact that it has your old married name on it leads me to believe that they tried to serve you at an old address....a lot of debt collectors do that on purpose because:
1--they know they wont actually find you there, so you wont show up for court.
2--they can still claim to the court that they served you.
They do that so they can get a default judgment against you. It is not legal, but most people dont know their rights under the law, so once they get that judgment, the average person doesnt know enough to fight it.