* It has a chilling effect: less disputes are filed
* employees prevail less often
* when employees do win the employee portion of the award is less than standard litigation
https://facesofforcedarbitration.com/wp-content/uploads/2019...
There's also numerous stuff that should, IMO, fall into class action, but gets divvied up in forced arbitration, to the point where it isn't worth the time and expense for the individuals in the class to continue to pursue justice. (Although there have been some novel DoS style mass-arbitrations … that's more of a means of trying to force the corporations hand into a normal class action, and towards justice.)
Normally the reasons cited for arbitration are things like "the courts are slow" or "the courts are expensive" or "the courts are overwhelmed" — but you could still just do arbitration at the time of dispute with those. Saying that forced arbitration is better from these arguments is non sequitur.
There's also a conflict of interest between the chosen arbiter and the company. (And conflict of interest is independent of bias; a good arbiter can very well be unbiased, but it is easier for everyone involved to believe that if there isn't a conflict of interest.)
So let her opt-in. Why force it?