I disagree with you, unless the girls have been physically abused or have mental issues (a real possibility considering who their father is and his family) there is no reason why they couldn't adapt pretty quickly. But they do need to be exposed to other people so that they can learn and develop social skills, and that has to be done soon, especially for the older girl. Learning those skills once you are an adult is extremely difficult if you don't have them by then.
The girls have a different life experience from most people, that isn't the issue you think it is since so does everyone else, and everyone else gets by just fine. I think the main issue the girls are going to have is an ingrained "us v the outsiders" mentality (this is what was causing the "odd" behaviour observed by the Berkeley cops - it wasn't something sinister), and for them it will be all to easy to slip into another cloistered world, which is probably what is happening to them now. I think that environment has been constructed for their mother but they will get sucked into it as well even though it is not in their best interests, since they have no choice in the matter and in any case are not sophisticated enough to know different. Their needs are going to be very different from what their mother needs and at some point the family is going to have to decide who is more important if they stay together: Jaycee or the girls, and go on from there. Sacrifices will have to be made by someone, and IMO it is not right that it should be the young ones.