Susan is mostly asking about Hanma’s name to set up the last panel, but my excuse for it is that she knows immortals choose their own names, and that it might tell her something useful about Hanma.
I mean, really, speaking of cultural sensitivity, immediately questioning someone’s name?
Also speaking of cultural sensitivity, Hanma is meant to be overly enthusiastic, immature, and unintentionally insensitive in a number of ways. She might, MIGHT, be partially inspired by how I was when I discovered edgy anime and Japanese culture as a teenager in the 90s (Gundam Wing was SO EDGY you guys they said “hell” and stuff).
She’s more extreme than I ever was, but being overly enthusiastic about using “cool Japanese words” was something I can’t claim I never did. Shocking, I know, what with early EGS comics and some of the times I wanted to show off what little I learned while failing to learn Japanese (though I still like that I know how to say “I don’t understand Japanese” in Japanese).
Having mentioned in advance my intention to name her "Hanma" (and the part where a "Hanma 1/2" joke clinched it), people have had the chance to weigh in on it.
My understanding now is that it should actually be pronounce like "hammaa", and is basically just the word "hammer" pronounced with Japanese phonemes. A Japanese "R" is very different from an English "R", and some would say it sounds closer to an English "L". This is why you'll sometimes see inconsistent translations of Japanese words with "R" in them, as some will favor "R" and others "L" when translating, or choose one over the other depending on a given word.
Anyway, most Japanese characters stand for two letters and include a vowel sound, one exception being the characters for "N". I've been told the "N" character is basically there for that reason (so it can immediately be followed by "ma" instead of another vowel being in there, and there is no character for just "M" on its own).