A couple of years ago, Marilyn Lange (it rhymes with tang) was back in her native New Jersey and going to secretarial school. Pretty blah. Then, on a whim, she went to Hawaii - via a tour - and stopped at Waikiki, where she met a young man who caught her fancy. She's been in Hawaii ever since, not because she's so crazy about the islands ("It's hard to get motivated here") but because Marilyn - no women's libber - frankly admits that her man's a very important part of her life: "I love being in love, and I'm willing to be a little slavish in order to make my guy feel good." She and Kip, her boyfriend, share an apartment in Honolulu - "We split the rent, because it's dumb for the man to have to pay for everything" - and they also work together, on a big old Chinese barge that's been converted to a restaurant. Marilyn is a cocktail waitress; Kip works the piano bar, playing and singing. Marilyn makes fairly good money - 40 bucks a night in tips, she says - and she enjoys the job because she's a people watcher: "After you do this for a while, you can tell by their accent what kind of tip people are going to leave. Like, Australians and Canadians don't tip the way Americans do; but then, people from New York don't tip the way L.A. people do, either." While Marilyn waits on tables, Kip plays Elton John tunes if there's a young crowd in the place; if it's an older group, he'll sing something like The Impossible Dream. Marilyn gets a kick out of the customers' reactions to her man: "The ladies just melt in front of him. I don't mind if they're five years old, or seventy-three, but if they're in between and pretty, then I do get a little jealous." On nights when they don't work, she and Kip like to go down to Kalakaua Avenue, which runs through Waikiki, and watch the tourists and the beachcombers. When she's got some daylight hours to fill up, Marilyn's likely to be on her lanai - that's Hawaiian for balcony - talking to her tomatoes and spinach plants; she also likes to crochet and hook rugs. As for the folks back home, Marilyn reports that although her grandparents raised an eyebrow or two about her liberated lifestyle, her parents are too wrapped up in their own thing to worry about her much: "My mother calls periodically to say 'How are you, my darling daughter? Are you sure you're OK?' - but now that all three of us kids have left, they've bought themselves a farm in Connecticut and they're having a second honeymoon." In case her grandparents are still concerned, Marilyn probably won't stay in Hawaii forever; after her relationship with Kip has run its course, she says she'll most likely head back to the mainland and check out some of her favorite places (Aspen, for one). Loyal as she is to the guy she's going with, she also knows something about the impermanence of relationships: She was married at 18 to a musician in a popular East Coast rock group ("It's really dumb, but I just keep getting involved with musicians"). It didn't last, and she has no plans to try matrimony again. In fact, Marilyn has no specific long-term goals. At presstime, she was about to go back to school and learn accounting; and she was thinking of investing her Playmate fee in some land. But she says - and it's like her to put herself down in a humorous way - "I have to grow up more before I decide what I'm going to do in the future." Well, she already looks pretty grown up to us.