Any previous offence within 10 years will result in a disqualification of at least 36 months.
If the Court takes the view that an offence is "so serious" that it can only be adequately punished by way of a prison sentence, then the Defendant can be sent to prison, even on the first offence. Clearly, "so serious" will depend upon the circumstances of the incident and the alcohol reading. Custodial sentences would normally be considered at readings of 116 ug breath / 265 mg of blood or 355 mg of urine.The Court will consider both aggravating and mitigating factors. Aggravating factors will increase the length of a ban, and could include lack of co–operation, having children in the car, being involved in an accident etc. Mitigating factors can reduce the severity of the penalty and can include a previously good record, co–operation with the Police, early plea, but with how you've described the events I'd be surprised if she doesn't get a custodial sentance (my opinion only).