Nodoka is Ranma's mother, and she's genuinely devoted to him—though she hasn't actually seen either him or Genma in over ten years. That separation happened because Genma decided to take Ranma on a training journey, convinced that a doting mom would only get in the way. He made a contract with Nodoka that he'd raise Ranma to be a "man amongst men," and if he failed, both he and Ranma would have to commit seppuku. Pretty heavy stakes.
The problem is Ranma's curse turns him into a girl whenever he gets splashed with cold water, which creates an ongoing mess whenever Nodoka shows up. She ends up seeing "Ranko" (Ranma's female form) and Mr. Panda (Genma in panda form) everywhere, and everyone's constantly hiding from her. It's clear Nodoka really does just want to see her son again—the whole situation eats at her.
Eventually though, especially in the manga, Nodoka actually finds out about the curse. And here's the thing: she takes it way better than Ranma and Genma expected. By that point, she'd already started putting two and two together, realizing that Ranma and Ranko were the same person all along. Once she knows the truth, the fear and secrecy basically fall away.
Content compiled by AnimeList.moe from publicly available sources.
