It's actually
Pamelyn Ferdin.
Very good! She was also the original Lucy in the Charlie Brown specials and - my next hint was going to be - she made Jan Brady cry.
She had a remarkable career as a kid and seemed to be everywhere and on every show.
Here's her filmography from her website:
240-Robert 1979 Nikki
Andy Griffith Show "Bazaar" 1965
Andy Williams Show 1966
Apple's Way "The Flag" 1974
Baby Makes Three "Pilot" 1965
Banana Splits in Hocus Pocus Park 1972 Susie
Baretta "The Runaway" 1977
Beguiled, The 1971 Amy
Bewitched "Eat at Mario's" 1965
Bing Crosby Show "Manpower" 1966
Blondie 1968-69 Cookie
Bob Hope Chrysler Theater "City of LA", "Free of Charge" 1966
Boy Named Charlie Brown, A (movie) 1969 Lucy Van Pelt
Brady Bunch, The "Will the Real Jan Brady Please Stand Up?" 1971
Branded "A Proud Town" 1966
Breaking Point "The Summer House" 1964
Charlie Brown Goes to Camp (TV) 1972
Charlotte's Web (movie) 1973 Fern Arable
ChiPs "Rustling" 1978
Christine Jorgensen Story, The 1970
Curiosity Shop 1970
Custer "To the Death" 1967
Daniel Boone "Requiem for Craw Greene" 1967
Danny Kaye Show 1966
Dating Game, The 197?
Daughter of the Mind (TV) 1969
Death Valley Days 19??
Delphi Bureau, The "Merchant of Death" 1971
Detention (TV series) 1999 Shelly Kelly
Doctor Kildaire 1973
Dr. Seuss: The Cat in the Hat (TV) 1971 Sally
Family Affair "Mrs. Beasley, Where Are You?" 1967 Melissa
Family Affair "No Uncle is an Island" 1969 Jennifer
Family Affair "The Birds, the Bees, and Buffy" 1967 Wendy
Family Affair "The Joiners" 1971 Shirley
Flying Nun, The "Cousins By the Dozens" 1969
Flying Nun, The "The Reconversion of Sister Shapiro" 1968
Forgotten Man, The (TV) 1970
Gene Kelly Special 1968
Green Acres "Instant Family" 1968
Gunsmoke "The Money Store" 1968
Happy Birthday, Wanda June 1971
Heidi's Song 1982 Klara
High Chaparral "For the Love of Carlos" 1969
High Chaparral "No Bugles, No Drums" 1969
It Was a Short Summer, Charlie Brown (TV) 1969 Lucy
Jerry Lewis at the Greek Theater 1968
Jesse James "A Burying for Rosie" 1966
John Forsythe Show, The 1965-66 Pamela
Lassie 1971-73 Lucy Baker
Littlest Hobo, The "The Babysitter" 1964
Love American Style "Love + The Instant Father" 1975
Mad Mad Scientist "Pilot" 1966
Mannix "Fly Little One" 1970
Marcus Welby, MD "A Portrait of Debbie" 1971
Marcus Welby, MD "The Tall Tree" 1973
Mephisto Waltz, The 1971 Abby Clarkson
Miles to Go Before I Sleep (TV) 1975
My Three Sons "Fly Away Home" 1966
Never Too Late 1965
Night Gallery "Brenda" 1971 Frances Anne
Odd Couple, The "Bunny is Missing Down By the Lake" 1971
Odd Couple, The 1972-73 Edna
One and Only Genuine Original Family Band, The 1968 Laura Bower
Paul Lynde Show, The 1973-74 Sally Simms
Play It Again, Charlie Brown (TV) 1970 Lucy
Project UFO "Sighting" 1978
Psychiatrist, The "The Private World of Martin Dalton" 1971
Reluctant Astronaut, The 1966 w/Don Knotts
Road West 1966
Roman Holidays, The 1973 Precocia
Sealab 2020 (TV series) 1972-73 Sallie
Second Hundred Years "Luke's First Christmas" 1968
Shazam! "Thou Shall Not Kill" 1974 Lynn Colby
Sigmund and the Sea Monsters "Puppy Love" 1976 Peggy
Smoke (TV) 1970 Susie (Disney Wonderful World of Color movie)
Space Academy 1977-79 Laura
Star Trek "And the Children Shall Lead" 1968
Steve Allen's Hollywood Bowl 1970
Stranded "Pilot" 1966
Streets of San Francisco, The "Runaways" 1977 Chris Cavanaugh
These Are the Days 1974-1976 Kathy Day
Toolbox Murders, The 1978 Laurie
Tree Grows in Brooklyn, A (TV) 1974
Valley of Mystery (TV) 1966
Vegas "Serve Volley and Kill" 1978 Katie
What a Way to Go 1964
What's the Matter With Helen (TV) 1970
Woody Woodbury Show, The 1968
You're in Love, Charlie Brown (TV) 1971