She achieved early fame as a child actress and through her association with Paul McCartney; she has worked extensively in film and TV throughout her career.

[1] Her father was a consultant in blood and mental diseases at the Central Middlesex Hospital, as well as being a broadcaster and the author of notable medical articles.

Her British TV appearances included three episodes (1956–1958) of the ITV series The Adventures of Robin Hood and as a panellist on the BBC's Juke Box Jury.

Asher appeared in Roger Corman's The Masque of the Red Death (1964) with Vincent Price, in Alfie opposite Michael Caine in 1966, and in Jerzy Skolimowski's Deep End (1970) with John Moulder Brown.

Another notable radio broadcast was in The Further Adventures of Sherlock Holmes in 2002, in the episode "The Peculiar Persecution of Mr John Vincent Harden".

In 2006, Asher starred in the Richard Fell adaptation of the 1960s science fiction series A for Andromeda, which aired on the British digital television station BBC Four.

Asher co-starred in the 2008 ITV drama series The Palace, filmed in Lithuania; she played Queen Charlotte, mother of King Richard IV.

In August 2008, Asher appeared with other showbusiness personalities in the reality TV talent show-themed television series Maestro, broadcast on BBC Two.

In the summer of 2013, she played Lady Catherine de Bourgh in Pride and Prejudice at the Open Air Theatre, Regent's Park.

Asher has written three novels: The Longing, The Question, and Losing It, and published more than a dozen lifestyle, costuming, and cake decorating books.

McCartney wrote several Beatles songs inspired by Asher, including "And I Love Her", "We Can Work It Out", "You Won't See Me", "I'm Looking Through You", "What You're Doing", "Things We Said Today" and "For No One".

The couple announced on Christmas Day 1967 that they were engaged to be married, and Asher accompanied the Beatles and their partners to Rishikesh in early 1968 to attend an advanced transcendental meditation training session with the Maharishi Mahesh Yogi.

In mid-1968, she returned to London from an acting assignment in Bristol earlier than expected and allegedly discovered McCartney in bed with Francie Schwartz.