WHERE in her contract is her action on her own time attending a rally forbidden?

Etc.

I'd hire the best labor-relations attorney, have him/her do an intense review of her contract/see if there is precedent for their actions and if all is "GO" sue the city fully into bankruptcy.
I mean, I wonder if they'd do this if they found she attended a gay pride rally cross-dressed. Or is a member of the Ku Klux Klan holding cross-burnings in her back yard.

DOUBT IT.

But support Trump on your own time and get fired.

SUE FULLY INTO BANKRUPTCY.