It’s the end — and the beginning — for Marlo Thomas who wound the five years of “That Girl” with a women’s lib-themed seg and now plotting a bigscreen feature featuring femmes freedom. She’s also got that “Sad Nun at Synanon” in the works. One thing’s certain, says Marlo, “I don’t have to rush into anything. But I will be making feature announcements soon.” She celebrated the five successful years of her TV’er with a giant party Saturday night on the familiar stages at Cinema General, received the 300-plus guests with series costar, and often offscreen date, Ted Bessell. P.S. the series ends with their status quo — engaged but no date set to wed … “Girl” producers Saul Turteltaub and Bernie Orenstein m.c.’d the party which included 10 minutes of mis-takes. “Gifts” to Marlo and guests included a St. Christopher medal to Danny Thomas — and a Danny Thomas medal to St. Christopher; a visit to the newly enshrined Marlo Thomas Room in Danny’s new, million-$ hideaway featuring five healthful minutes in the Danny Thomas Steam Room which features no pipes, no rocks — just steam coming off two sweaty camels; and the original pilot script of “That Girl” complete with a rejection slip from the show’s first proposed star — Terri Thomas! … Fast fade-in to today as the Museum of TV and Radio launches its “She Made It” three-year program saluting 50 women who were pioneers in broadcasting fields. Among them — Marlo Thomas. The Museum will screen works from the 50 femmes — there’s plenty to choose from Marlo’s rich dossier.