Well, she’s not admitting to being an intentional saboteur, but Yoko did confess that her relationship with John came at a cost to their potential. Via Contact:
In a way, both John and I ruined our careers by getting together, though we weren’t aware of it at the time. My initial reaction to rock music was, “Oh dear, how simple can you get?” At first I thought John would carry on with The Beatles and I would do my own things, but he felt it wasn’t right that we were working separately, that the union we had might not last, because of the pressure of the world.
So she’s implicitly saying that John’s career would have been different (and better) had they never married. Fair to say that she’s suggesting The Beatles may never have broken up if it wasn’t for her “how simple can you get?” disposition? That question doesn’t even matter, though; based on her quote, an army of anti-Onos all over the world just shouted “Told ya so.”
[Pic from Yoko's set at Øya Festivalen '06.]