ALDERSON, W.Va. (AP) _ A member of the notorious Charles Manson ''family'' says she has strong personal and political reasons for wanting to stay in prison when her mandatory ''good time'' release date comes up later this month.

''It's not that I'm institutionalized,'' said Sandra Good, one of Manson's early followers. ''Anybody who has ever been in prison would rather be free to do things such as go to the beach, walk in the woods and see their children.

''It's just that I want to be where my family is, and my family is in prison.''

Ms. Good said she preferred her cloistered existence at the federal women's prison here to a life in what she calls ''the bigger institution'' outside.

The 40-year-old former Southern California surfer girl has served nearly 10 years of the 15-year sentence she received in Sacramento, Calif., for conspiring to mail death threats to corporate officials she accused of polluting the planet.

She was arrested when FBI agents searched the apartment she shared with another family member, Lynette ''Squeaky'' Fromme, who had been taken into custody for pointing a pistol at President Ford.

Ms. Good and Ms. Fromme, who was sentenced to life in prison, have been serving their time at Alderson, a medium security prison that resembles a college campus. They see it somewhat differently.

''In a way, this place can be viewed as our convent,'' Ms. Good said in an interview at the prison. ''We're like nuns, working toward Earth balance.''

The two women keep their heads covered in nun fashion; they wore bandannas during the interview.

Ms. Good was dressed in blue, symbolizing ''clean air and water.'' Ms. Fromme was clad in red, ''for the animals and earth colors.''

''Blue,'' as Ms. Good called herself, elaborated on her reason for not wanting to be released.

''Thought can be as important as deeds,'' said Ms. Good, her blue eyes matching her outfit. ''By staying inside where my family is, I keep myself outside of thoughts that are dedicated to money, power and approval. I keep myself in the thought of ATWA (Air, Trees, Water, Animals), the thought of life.''

Ms. Good and Ms. Fromme work as groundskeepers at Alderson. They live in separate dormitories but see each other daily.

Neither woman was connected with the Manson family murders of actress Sharon Tate and eight other people in 1969. Manson and four members of his counterculture clan, who lived on an abandoned movie set near Los Angeles, are serving life sentences for the wanton killings at two houses in a luxurious Hollywood Hills neighborhood.

Ms. Fromme and Ms. Good maintained they were in telepathic communication with Manson. They also said the actions for which they were imprisoned, and the killings themselves, were designed to protect ATWA.

''We all need ATWA to survive,'' said Ms. Good. ''So, you can see that the killings were done in self-defense. Also, they were done to prevent the world from being blown up, but that's all I can say about that.''

Ms. Good said she would like nothing better than to be with Manson again. She hasn't seen him since his 1971 trial, although she has had permission to write to him.

''Manson is ATWA,'' she said. ''He is the balance, I know this in the depths of my soul; also, I have a child by Charley.''

However, she said she didn't know whether she would try to see Manson after her scheduled March 29 release. Prison officials have told her that doing so would violate her probation, she said.

''I really don't know what I'll do if I'm released,'' Ms. Good said. ''When I was sentenced I made a statement in which I told the judge I couldn't live in society without making some moves to stop what I see is going on. I still feel that way.''

What is going on, she added, is a steady poisoning of the air, water and land. The destruction, she declared, is being done in the name of profit, motivated by a love of money.

Warden Gwynne Sizer is familiar with Ms. Good's philosophy. Nonetheless, she said the Manson family member would be returned to the Sacramento area upon her release.

''We've talked,'' the warden said. ''I've told her it's out of my hands. She was sentenced under a law whereby she gets 10 good days each month for good behavior. She's never been in any trouble during the time she's been in prison. Therefore her time is up; she's got to go.''

Ms. Good was reluctant to discuss the nature of any current contact with Manson.

''I don't want to talk about it,'' she said, fingering a necklace that had been braided from wool.

Asked about the necklace, which appeared to be new, she smiled and said: ''Charley made it. He makes them out of his socks. He's very good with his hands.''