Cats do generally work out their differences if given enough time. It's always best to confine the "new" cat to the smaller space, because bringing a new cat into a living situation is a "violation" of the resident cats' territory. It's better that they give up only a little territory rather than most of it to the new cat. Never let the resident kitties into your cat's territory (the bedroom), and they'll eventually forget it was once part of their territory.
One way to get the other kitties more familiar with her is to buy a big wire animal crate. When the other kitties have the run of the house, put the crate your kitty in the big crate. Start out with the cage just outside the bedroom door (just barely into their territory). The other kitties can smell her, and get to know her, but can't hurt her. Do this for just an hour at first. If your kitty doesn't mind the crate, increase the time and move the crate further and further into the other kitty's space.
Eventually, you will see the other kitty's attitudes towards your kitty change. They will hang out by her cage, and may even lay down by her or interact with her in the cage. Then you can start having supervised visits into their territory. Eventually you will not need the crate, nor the supervision, and she will be part of the clowder (the name for a "pack" of cats).
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