Probably taught by some unnamed offshoots of the Iron Palm clan, left to drift after Qiu Qianren followed Yideng. That said, her qinggong was supposed to be quite decent. From ROCH chapter 10.
The three then utilized their lightness kung fu and hurried to the
southeast. The Ancient Tomb sect’s kung fu’s forte is lightness kung fu;
it could be classed as the world’s number one. Wanyan Ping’s martial
arts may not be anything special but her lightness kung fu was not weak.
How was it that the girl in blue green followed behind her without
breaking speed? When Wanyan Ping was going fast, she went fast, when she
slowed down, the girl slowed down, the gap between them remained
constant at one or two paces. Yang Guo was secretly surprised, “What
sect is that girl from? From her lightness kung fu, her skills are
higher than sister Wanyan’s.” He didn’t want to lead the two girls and
so slipped to the rear.