Earlier quoted context omitted.
It actually would be illegal in most of the EU (at the very least in The Netherlands) AFAIK. This is some "only in the US" level stuff (in the context of "The West").
Netherlands you could have 3 month probation (I think??) or most companies may start employees on fixed-term employment contracts (6/8/12 months) before becoming permanent which is very common (Netherlands had a rule where you could have 3 fixed term contracts, up to 24 months total, before becoming a permanent employee) so they could've hired her on a 6 months contract and simply not renew it :)
also, you can't be just fired for performance reasons right away -- you need to first do a documented improvement plan and you need to at least try to move the employee to a different part of the company.
if she was in the netherlands, she could easily sue CF for wrongful dismissal.