The credit line for her first full-length feature film, "My Brilliant Career," read "Gill Armstrong," which sounded more androgynous than she had expected. So her name on her latest film, "Starstruck," which opens here today at the Key, reads firmly, "Directed By Gillian Armstrong." That's because she is proud of being a woman filmmaker and didn't want to confuse anybody.

"I did it because people over here thought Gill was a boy," she said. "But I've noticed that another friend of mine, Phil Noyes, is now Philip. A lot of Australian filmmakers are changing like that. When we start using middle initials, then you'll know we're really getting pretentious."

Armstrong, at 32, is among a handful of filmmakers who have created an industry in Australia during the last 10 years that has gained enormous recognition and popularity. Being so new, the Australian industry is not restricted by the bureaucracy and large budget exclusivity of Hollywood, and its movies have been hailed as original and well produced. Directors like Armstrong work independently, financing each picture as it comes along, choosing projects they like and working with comparatively small budgets.

"After 'My Brilliant Career' came out in 1980 , my agent introduced me to some Hollywood producers," Armstrong said during a recent visit to Washington. "The first one asked me what sort of films I'd like to do. I said 'any sort,' and then he said 'what about a thriller?' and I realized I didn't want to do that, and I didn't want to do almost any kind of film they would name."

Instead, she spent over two years after finishing the critically acclaimed "My Brilliant Career" looking for the right project. One of those years was devoted to developing a script with a writer that never worked out, an investment of time and money she said she will not repeat. "I won't be that stupid again," she swore. "Now I'm working on three ideas at the same time, and maybe one of them will work out."

She wanted to do something completely different from "My Brilliant Career," which was set in the 1890s and graphically pictured the social straitjackets placed on a woman with an independent mind.

"People thought I wore my hair in a bun and stayed home embroidering and listening to Schumann," she said. In fact, she has recently cut her long bleached-blond "surfer girl" hair into a punk shag, and on this day was wearing a large, fuzzy blue sweater-dress decorated with colored beads, a black-and-white polka-dot blouse, black tights and blue suede shoes. She is a fan of rock music, which is one reason "Starstruck," a new wave musical comedy, appealed to her.

Having gone to art school for four years, she said, "I have a lot of pretentious ideas. I like to think of myself as an artist. My films are an expression of myself, but also, I hope, of political and social concerns."

Her first plan for her second feature film was a serious piece of social realism on youth unemployment. The script that failed was written by a "young communist," whose politics, however acceptable, were not enough.

"Starstruck" deals with youth, but it is anything but serious. The main character is a young woman from a working-class family who wants to be a new wave singing star and, with the help of her recklessly daring younger cousin, brazens her way onto a television show. At one point her cousin persuades her to walk a tightrope strung between two office buildings while wearing an artificial torso of huge breasts. In another scene she is invited to a party that turns into a water ballet with a chorus line of homosexual men in bathing suits. The auditions for those parts, she recalled with a giggle, were a switch on the usual cheesecake cattle call, with a woman director and choreographer reviewing the beefcake. Most of the swimmers are university athletes.

"It's totally frivolous," she said about the movie. "But there was something that touched me about the people. When I was interviewing actors, I knew some of the very heavy ones would ask why on earth I was doing this frivolous film, so I prepared an answer for them: It's in praise of free spirits. That shut them up."

Unable to find her leads among the established actors in Australia, Armstrong cast two unknowns, and for the first time in her life found herself a mother figure. "I've always felt like a young person, you know--a hip young filmmaker. And here I was telling people to get to bed early and eat properly. I felt old for the first time.

"When we hired Jo Kennedy (who plays the female lead) she was living in a warehouse with 20 other unemployed rock musicians and thought that was absolutely great. When we moved her to Sydney for the filming we had to say, 'Please get an apartment, and a telephone.' She thought that anyone over 25 was not worth talking to, and she was so unhappy when she first came on the set."

In "Brilliant Career" the heroine tells the man she loves that she will not marry him because she wants to be a writer and she can't do both, a scene that Armstrong said was partly misconveyed because she cast too appealing a man as the rejected suitor. "I admit failure in that area," she said. "You were meant to see that they were not really like spirits, and that was the main reason she wouldn't marry him. But it was also the 1890s, and women then faced having a baby a year. She couldn't face that either."

Armstrong has neither husband nor babies herself, and believes it would be very hard indeed for her to manage while being a film director. "When I make a feature film I just say goodbye to my friends for three months. It takes that kind of commitment. When I finish I find I don't even know what's happened in the world because I haven't been paying attention."

One of her eccentricities is that she doesn't drive, which is as unusual in Australia as it is here. "I did drive for two years, but I'm not very good at it. I'm too passive and too aggressive. I would lose patience with parking, for example. For the benefit of humanity I decided to stop."