Logical Predication

Hello, while solving problems from OG, I stumbled upon 2 answer explanations that have left me quite confused.
I have listed them below, please guide me.

1. https://gmatclub.com/forum/despite-the- ... 37482.html

the proportion of judges and partners at major law firms who are women has not risen comparably

CORRECT: The pronoun "who" can only refer to people. Therefore "firms" cannot be antecedent of "who". Hence "who" is not ambiguous.


2.
https://gmatclub.com/forum/as-an-actres ... 20808.html

Stella Adler was one of the most influential artists in the American theater, who trained several generations of actors including...

PROBLEM: The second modifier is incorrect. "Who trained several..." should be touching Stella Adler as well. Instead it's modifying "American theater", which doesn't make any sense.


My doubt here is the usage of who
In what situations is it acceptable to use who after a thing?

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