So, because she knew that that other woman would interpret her strength as a threat, she pretended to be a cripple?
Really?
Seems like a stretch...
According to another commenter, the author retconned MC's mom into being strong while writing later parts of the story, which is why this feels so disconnected to her earlier depictions.
It genuinely does not make much sense that no one knew about her strength, in a country where reputation and strength are famed and judged. How could she be the country's strongest, yet no one remembers her as that?