She is calling him a her because she’s really hurt and when people are hurt/ jealous/ angry/ uncertain about things they will say the most hateful and hurtful things. So she’s saying these things because it’s the most hurtful thing she can do towards Archie.
Sometimes people don’t realize the extent of their words especially when they have never been through what the other person has gone through. Explain to her that it is not okay for her to be attacking Archie this way. Ask her “what about this bothers you so much?” “I need you to accept that what happened in the past is in the past and if you can’t move on from that, there’s nothing you can do about it”. “What’s are you afraid of? (Reassure her). Talk it through and if she continues to talk about Archie like this.
Then you have a few choices.
A) You marry her and potentially have to end your friendship with Archie.
(In your fiancés mind she feels very insecure about what happened in the past and is afraid it would happen again and that two friends with a past are still near each other. When a couple marries, occasionally some friendships end because the partner is not okay with the friendship. If you marry and keep Archie close, the arguments will be endless (because she doesn’t trust Archie and you around each other.) and since you gotta make a marriage the priority well :/
I think she sees it as a from a betrayal that someone you hooked up with is still your friend. Some people just can’t accept this.
B) Marry her and potentially have her continue to insult your friend. This would probably end the relationship because you’d defend your friend and this would validate her idea that you love him more than you love her. Down the line this will wear out and end things
C) Give her an ultimatum. Tell her that you only see Archie as a friend, that you would never hook Up again because she (your fiancé) is the only one you love. Tell her that Archie is one of your closest pals and are not willing to put up with these type of insults for the rest of your marriage so if she doesn’t stop, you are going to break off the wedding. I think she might stop (sometimes people don’t learn things until they are given and ultimatum). (Make sure to investigate if she has a past saying homophobic things).
Sometimes couples will marry knowing their partner is racist (I’ve seen it happen). And their marriage still works (idk how). Personally I wouldn’t recommend it but ultimately it is up to you.
D) End things. Ask yourself this, “If in this second she stopped insulting Archie Do I still see her the same way?” Think about that and if it’s something that cannot accept- end things because you will bring this up down the line when you have other arguments.
Im sure you’ll be wondering, “Is she really against transgender people or was she just hurt?” It doesn’t excuse the reasoning but it can certainly help you make decisions. I’m not sure how to figure this out except by asking those that know her.
Keep in mind Archie will be a stain in the relationship because she’s insecure about what could happen between the two of you. Of course you wouldn’t do anything because you are not interested in men but it’s difficult for some people to understand this. When someone is insecure they can assume all sorts of delusional/ crazy things.
My main tips here are to see if
1) she has a past do being transphobic (this can give you an idea of your how your future wife will be.
2) Reassure her that you love her and want to spend your life with her.
3) Mention that you will not marry her if she continues to misgender your friend nor anyone else. Tell her that you just cannot marry someone that is against the LGBTQ community because that is one of your morals / standards that you will not for her.
4) Keep in mind Archie May be the cause of many arguments down the road. (When you argue in favor of Archie this will fuel her idea that you love Archie more than her so something’s gonna happen here. Either you’re gonna distance yourself from Archie or she’s gonna have to fun a way to accept this (maybe try couple therapy?)