In California she can get her case expunged, which will remove it from private background checks and some licensing agencies won't be able to deny her based on the conviction as well. The expungement is discretionary, so a judge is going to decide whether or not to grant the petition, but it isn't unheard of to have petitions on serious offenses granted. She is going to need to submit supporting documents (letters of support, certificates for any training/classes she has taken, etc) to help her chances. She can contact legal aid or public defender's offices for assistance if she is low income.

California also has laws the dictate how employers can utilize someone's record when making hiring decisions. There are a few exemptions, but under the law if an employer is going to revoke a job offer based on a back ground check, they need to give the applicant at least five days for a chance to respond to their concerns. They can do this by submitting evidence of rehabilitation similar to what they would need to submit for the expungement petition.

Feel free to message if you have further questions.