She is beautiful! Please find her girlfriend.
Neutering in guinea pigs only affects their ability to make babies, it does NOT affect their behaviour in any way - it certainly does not calm them down and it will not prevent them from falling out!
You can NEVER have two boars with any amount of sows; there will be inevitably bloody fights. I know that some (bad) breeders do this to ensure that their girls get pregnant asap, but it is an extremely stressful situation for any of the piggies involved and the trauma in those winding up in a rescue often runs deep.
Here is more information about possible boar bonds:
http://www.susieandpigs.pwp.blueyonder.co.uk/optionsmenu.htm
Here is more information about all aspects of neutering:
http://www.cavyspirit.com/neutering.htm
PS: Rabbits and guinea pigs should NOT be kept together; they have different food and vitamin requirements, apart from the fact that an intended or unintended kick from a rabbit can seriously injure or even kill a piggy.