Unless you're egregiously bad at your job, getting fired for performance should never be a surprise. She says she'd had nothing but positive performance reviews until the day she was fired, so unless you think she's lying I see two possibilities:

1. Her performance was subpar but Cloudflare told her to keep doing what she was doing.

2. Her performance was fine but the Cloudflare are full of shit.

Either way it's not a good look for Cloudflare.

Pretty much. Not for anything short of total malfeasance or horrible misbehavior.

Layoffs happen. Welcome to tech. Just say it's a layoff, and everybody will get on with life.

However, trying to fire someone for performance short of 12 months smells like somebody was told to try to claw back or limit signing bonuses, relocation allowances, stock grants, and promissory estoppel claims.

It's a VERY, VERY bad look for Cloudflare who, up to this point, I had decent vibes about from dealing with various employees.