I am guessing that she is talking about the fact that she felt that you didn't help her during your visit, be it washing up, making coffee, cleaning, even laundry which to me is quite strange!
When you are a guest in someone else's house, it is not always easy to help with things in case you do it wrong! Why on earth did she not say to you either before you went or when you had arrived something like "Mum, while you are here staying with us, would you mind doing xyz?" . Maybe MiL just walks in and takes over so DD just assumed that while you were there, you would do the same - even after a 5 and a half hour drive!
I'm afraid that if you go and stay at someone elses house, you are a guest and the host does most of what is needed - seems DD got the idea it should be the other way round!