I've got a group of 4 sisters living together happily in a big shed adjoining a fenced off patio, which they have access to for a couple of hours morning and evening. They are now 4yrs old and have never been split up. The loppy rabbit in my sig was their mum - she had to be split from the group for an operation, and after recovering for a month it was too difficult to rebond her with her daughters, so it's important they aren't split up for any reason.
Mine aren't spayed and they do have phantom pregnancies from about March till September. I leave the nest alone for a couple of weeks and they lose interest, although during that time they all protect the nest which just one of them has made, which is very sweet - I clean out around it and they pat it with their front paws and look at me all worried :lol:
The only thing that makes mine fight is food - they see me, they think I have food and it's usually Primrose - greedy girl - decides to chase her sisters away or leap on them and give them a good telling off, so she can have it all :roll: That's nothing to do with them being female, it's more down to personality - Zinniea is very calm and sits by my feet waiting for food while her 3 sisters tear about the place trying to chase each other away :lol:
The key to stopping the chasing and dominant behaviour is lots of space, with boxes, chairs, etc for them to jump onto, or run through - plus I always wear wellies so I can put a boot in between Primrose and her victim - she looks very ashamed then naughty madam
My main worry with your mum's situation would be that rabbits are notoriously hard to sex correctly when young - even vets get it wrong - and time and again on the forum I see people crying about their rabbit being pregnant because they didn't have 2 girls after all.
I adopted my group from rescue when they were all fully grown, but rescues do have litters of slightly older babies in too - especially around Easter time sadly - it would be lovely if your mum could give them a home as it sounds like she's going to take good care of them