I am going to first say that the name calling is not Ok! She can't expect to have a grown up conversation with you, if she is going to act like a child.
I would agree with the above post to say that she might see marriage as an entirely different entity than you do.
I am sure it hurts for her to know that you and your husband will be married and if she stays with you guys, that, that will never happen for her. While you may only see it as "paperwork" marriage can mean a lot more, even if you don't take it that way.
I have been in a similar situation, and although much like you my partner did it for the sake of the children. I was aware that it had a lot more social meaning behind it. If anything ever happened to her, her husband would have say and I wouldn't. If she was in the hospital he could see her and I could not. It was an indication to me of not only love, but of the idea that there was enough trust and long term commitment between them and that it was officiated and recognized, and though I may have wanted and felt the same way about her that he did, it was not recognized for me. That is probably very hard for her to deal with.
I don't know the details of your relationship with her or your husband. I was often frustrated, by the idea that he was the husband and I was often see as "oh, your just the GF". We couldnt change "paperwork" at that time, but we could change how people who didn't know the details saw things and that helped a lot. Instead of refering to me as her GF, my partner would call me her "partner" or "wife" I wasn't in a relationship with the husband so, if she is I am not sure how that will work for you, but for us people treated me differntly and had a little more respect for me, than they did when I was GF.
When things calm down, I would ask her to explain to you how she views marriage? If you can see where she is coming from without her BS than maybe you can make her feel more comfortable.
Just a thought I wouldn't down play the marraige as only being paperwork, I would up play the idea that you think is sucks that you can only marry one person, or that women can't marry or something like that...
I would also remind her when she calls you a traider or whatever...that straight people, and married people are not the enemy. Not marrying somone will not give others the right to marry, it only takes more rights away. What your doing by being open about your situation and still having people come to you to preform their ceremonies is giving them the oppertunity to open their eyes.
Best of luck to you!