I've always been aware of Loch Lomond, which was a pretty decent hit at the time. I've just listened to S'posin' which showed she had a very decent voice. That point about her stage presence could explain why she remained, effectively, a one-hit wonder. If she didn't make it big at the time, there's no particularly reason why she should go through a massive retrospective reappraisal. However, she clearly had the vocal talent to have been bigger.
i can't see how stage presence would affect the amount of listeners on last.fm, especially since i doubt anyone who would've actually been able to see her in her heyday is on last.fm. regardless, i think maxine's great, she had a wonderful voice. definitely seems like she's too unheard of, though, no matter what the reasoning.