HI, I understand what you are going through. I do not think you should put the blame on your new financee because that will only create resentment. I would stop if you want to. From the sounds of it you want to, but feel guilty. There should be no reason of guilt. It sounds as if you done everything you should have. Your fiancee has the right to feel as she does. At this point your ex is your ex now it is best to focus on your current relationship because then you may feel guilt for that and your actions will be counterproductive. I would tell your ex that you are in a new relationship and out of respect you need to stop helping her. If you choose to remain friends that is up to you, but should not be out of guilt and should be respectful to your new relationship without crossing any lines. A little help if you want is one thing, but too much may be crossing the line. I would look within and be true to yourself and your ex. Blaming your fiancee will only make things worse. Do what you feel is right and try to imagine how you would feel if your current fiancee was in your shoes.
I wish you well and please let me know if I can be of further help.