That's underselling her influence as an artist from her pre-Beatles period. She produced a handful of important avant-garde pieces and performances from the 60s in NYC and London and was a student and collaborator of John Cage, an extremely influential composer who has had dozens of exhibitions at MoMA. In fact she first met The Beatles to request a song manuscript for a Cage book.
She was also well connected to that world (she was invited to join the Fluxus community and artists like Marcel Duchamp attended her NYC loft parties) and quite ambitious, so there's a non-zero chance she would have become even more prominent had The Beatles association never taken place.
I have no interest in that world myself, but to say she was a nobody without The Beatles simply isn't true, she was definitely a rising star. A household name? Probably not, but possibly. An artist from that period that could be exhibited at the major international galleries, have her works studied in art schools? Absolutely.