5. seems moot. You describe she wanted to liquidate, she did liquidate, and it was 2020, but this is April 2021. So, all of that is moot, now. No need to work on rollover considerations.

"I had been sweating having to tell the client she was going to have a large tax bill but she had already been briefed by the Trustee."

If it hadn't lost value, she would be paying taxes on $300k, so she's a bit lucky. Although, I'd be willing to pay taxes on something 3x as valuable, of course.