Your male needs to be neutered before proceeding. Otherwise his hormones will prevent the bond from truly forming and will cause her to be more aggressive towards him. So, I would pause all bonding and focus on that first. Once he’s neutered, let his hormones settle for 3 weeks and then try again. Considering how badly they have been fighting taking a break is a good idea in general.
It is possible they aren’t a good match, but I have a strong suspicion that things will go differently once he’s neutered. When you restart, I recommend doing sessions in a very large space (at least 2 x-pens) that’s completely neutral, such as a friend’s house if possible. For all of my tough bonds the setting has been very important, and larger spaces can help the buns move around without feeling trapped or threatened by the other bun.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.