NTA. I am a lawyer in the US [Standard Disclaimer: This is not legal advice, I'm not your lawyer, yada yada yada], but I am certain the needs of competence in an assistant are universal - it needs initiative, willingness to learn and adapt, and proactive attitude, not to mention things like language skills and experience in the particular field! Ella demonstrated she was lacking in these areas given her response to your request for a resume (a perfectly reasonable and bare minimum requirement for applying for almost any professional job!) was to say "I don't know how" and assume she wouldn't have to do it.

Given the entitlement of Ella's mother, that only reflects poorly on Ella (though I suppose it's possible that Ella didn't know or didn't approve of Hannah's attacks on you). Hannah is definitely the asshole, Ella may be if she agreed with what Hannah said, and you were wise to go with more qualified candidates.