During termination the employee claims that his/her poor performance is due to alcoholism and claims that under CA law the company must give the employee time off for rehabilitation. Is this true?

No. Employers with 25 or more employee are required to reasonably accommodate employees who voluntarily come forward and ask their employers for time off for rehabilitation prior to a disciplinary action. (Labor Code § 1025) Once time off is granted as an accommodation, however, employers are not required to continue this accommodation time after time.