Gigi Ambardos of Allentown Pa., mounted the balance beam in a full press handstand in tonight's finals of the National's Capital Cup gymnastic meet at Old Mill High School and came off a winner in full twist dismount with a score of 19.20.

In between, Ambardos, 15, a 5-foot-1, 98-pound high school sophomore, did a switch leap, back walkover, numerous back handsprings and a front aerial with all the confidence of a professional athlete.

"I was a little worried," said the petite brunet as she smacked on a wad of bubble gum, adding that she came to this invitational meet expecting to get into the one of four finals.

Susie Van Slyke, 14, of Cherry Hill N.J., placed second to Ambardos on the beam with 18.45 points and came back in the evening's final phase, the floor exercises, to perform an elegant routine for the first place with 18.60 points.

"I should have been worried" said Van Slyke, who was fourth overall last year. "But I worked hard for this."

Clad in a pink leotard, Jackie Brummer, 15, of North Tonawanda, N.J., who had injured her ankle in practice for the vault, performed a Tsukahara full twist for 18.95 points and first place in that event.

Twenty minutes later Brummer took second on the uneven bars.