They can't force her to "snitch". She should set it for trial and they will not be able to identify her. They will want her to give up the individual who ran the light, but she should not do it! Ultimately, the case will be dismissed if it is not her.. It will take a little of her time, so don't do it again =) Good luck! She can avoid going to court by hiring an attorney.
Exercise your 5th amenment right not to rat out whomever the driver was. Your mother should consider hiring a lawyer such as our firm which respresnts individual such as her in this type of situation. Santa Ana Photo Citations are vigerously prosecuted so she definately needs someone on her side.
Feel free to contact us for a consultation. Iannelli & Associates, 949 729-3171 This answer does not constitute legal advice and no attorney client relationship is created. Every case has many facts which are different and distinctly theirs, make sure that you understand this is general information and it would be advisable to constact a competent lawyer for personal legal advice.