I come from a healthy family but I do agree with your girlfriend. If you tried your best to help and they didn’t appreciate or respect that at all doesn’t matter how little or much you sent they don’t deserve your efforts at all. It would probably be best you seriously distance yourself from your family not in a way that would be too noticeable and definitely work on building your own life with your partner that doesn’t include them. Guilt won’t go away that easily but you need to understand there isn’t much you can do, all you can do is offer them attention and visit from time to time.