If we're going to get technical...
Why would a ninja walk about in her training/fighting togs? I mean, from the way Meyah is described, it seems she's wearing the beloved 'ninja suit' that we see in films.
Secondly, according to what I've read, isn't a ninja supposed to be trained from birth? Also mentally conditioned to be loyal to and only to his Chonin and Jonin? I've read a few hints about ninjas being capable of voluntary bone dislocation and that its usually trained at an early age. When Ranma already expresses his strong ties to his father, that doesn't really make him prime 'unthinking killer' type of person.
Secondly, thanks to what Samantha pointed out, a ninja uses his brains (or her brains) before even clenching her fist. If Meyah were to go around walking like the ninja she is, and stalking in and out of shadows, wouldn't she draw more than a little attention?

Well, I know alot of what I've said may be erronous or downright WRONG, but here's my 2 cents.

Ranmania

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