L.,
Is this your 23 year old? If they have been married 3 years, I think this feller wanted a room mate rather than a wife. Seems as if he had his sights set on going to college and not necessarily being married. Had they gone together and planned to get married for a while before they did get married?
I agree with the poster who said that someone needs to talk to her husband and it needs to be your daughter. IF there is a breakdown in communication and he is determined to move on..than she is young enough, cut the ties. Alert every bill collector, landlord and even her boss to the situation. This way everyone in her circle will be prepared for whatever the future holds.
I would also suggest that your daughter continue to work so that she is building her own credit and what have you. If she were standing in front of me, I would tell her to close any and all jointly owned accounts with his name on them so he has no claim to her hard earned money. Has he moved out? Since she seems to be independant, I would suggest she also consider moving into an apt that suits her needs and solely her needs!! Not back with Mom and Dad!! I know it sounds like tough love, but if she did move back with you, this could upset your household and your younger children's lives.
Support her yes, but I have seen way too many of my friend's who have gone through similar instances wind up in feuds with their kids based on the failures of "what Mom said to do" when the married kids started talking about divorce and than got back together. She was obviously mature enough to get married and start planning a family, right? It will make her stronger and more leary for the next relationship she gets in.
This sounds like an example of getting married too young. L., she sounds like a hard worker who comes from and very loving family...I would have told her to go to school herself, maybe travel and discover the world and than worry about having kids and a husband later on. At 23, she has her whole life ahead of her still...that is what I would be encouraging.
Big HUGS to you, I wish I would have had Mom source to speak to when I was havign hard times like this!!