"I assume she already was in the midsts of a theatre career when she wrote those hateful thoughts."
She may have been in college, but the post might even slightly predate that. I think her professional debut was Ragtime at the Charing Cross Theatre, which was autumn 2016. She's still quite young - young enough that she was probably still a teenager when she wrote the post that has caused so much fuss.
I'm not making excuses for her, and plenty of teenagers manage *not* to carry around such appalling bigotry - but not every teenager has to grow up in the environment she grew up in. As I said somewhere else, it looks like her father is a real piece of work.