I have a Dwarf/Mini Lop bonded pair, but other wise all my Dwarf rabbits have been fine with other rabbits outside their cages, but not wanted to share their space with anyone.
If they are both girls and are getting along now that's great - spaying them will help save that relationship. Just like with us hormones can ruin things, especially at a certain age!I have Hollands, but have never had a Dutch, so I'm not sure of their personalities. I know different breeds can bond just fine, but it's all about personality and definitely has a lot to do with spay/neuter/temperament...
Good luck, look forward to some pictures and an update.