Unfortunately, as an at-will employer, your employer can change the rules of your employment at any time for any reason with or without any prior notice.
This stems from the employment at-will doctrine, which is codified in California Labor Code Section 2922.
"An employment, having no specified term, may be terminated at the will of either party on notice to the other. Employment for a specified term means an employment for a period greater than one month."
However, your employer cannot physically assault any employees, and if she were to do so, this would constitute battery, and could be actionable as a civil suit or a criminal matter.
Finally, your employer cannot make deductions from employee wages for $1 per minute for being past a 'grace period.'
This constitutes an illegal deduction from wages in violation of California Labor Code Section 221, and you should file a wage claim with the Department of Industrial Relations for the amounts illegally deducted from your pay.
You can file a wage claim using the forms available online here:http://www.dir.ca.gov/dlse/howtofilewageclaim.htm