Your frustration and anger will negatively affect your daughter more than the way your husband is behaving. She lives with you. You are her primary influence. Find a way to stop fighting with him. It takes two to argue. When a conversation appears to be headed for an argument, stop talking. Leave if you can. Say, we'll talk more when I'm able to be calm. Ignore all opinions. He has a right to them. His opinions do not mean that you have to change what you're doing. If he wants to change what he's doing that's OK. You'll need to accept it. You cannot change him.
I just went back to read your previous posts. It is obvious that your daughter did NOT just begin to have serious issues after your husband introduced his girlfriend. I suggest you are desperate to find an easy answer to your problems. Blaming the girl friend will not improve your situation. It only makes it more complicated and less likely for you to get any help.
I suggest that drawing her father dead in a coffin is indicative of feelings that have been long in coming to the surface. And.......it's just as likely that her relationship with you and your attitude towards her father is influencing her feelings as much as her father having a new girl friend.
I urge you to find a way to stop fighting with your ex. And above all do not share your feelings with your daughter. Do not let her see you mad and critical of her father and his girl friend.
If she's only been in the picture for two weeks, whatever behavior your daughter is doing now is not the result of her being involved. A child doesn't suddenly become a problem. I don't know what difficulties you're having with her but if she's repeating what the girl friend says and acting out because her father and the girl friend are critical of you, it's an indication that you don't have a good relationship with her. She won't go from being on your side to being on their side if there aren't sides to pick.
Try to look at what's happening from your husband's and his girl friend's view point. Find places in which you can agree. Be confident in your self so that you don't have to become defensive. Be willing to make some changes and definitely find ways to compromise. If you're not able to tone down your anger, get some counseling.