If your friend has a car of her own, has she checked her own insurance? Up until recently, almost all insurance policies covered the insured person (at 'third party only' level) for driving any other vehicle, with the owner's permission. Although some insurance companies no longer provide this cover, it still forms part of the majority of policies.
If she didn't have cover under her own policy, her position is rather dependent upon her relationship with her boss. If he's honest and supportive, he should be happy to write to the court (or, better, to appear before the court). However, he might be reluctant to do so because it's an offence to 'cause or permit' someone to drive a motor vehicle without insurance. The law regards this just as seriously as actually doing the driving. So the employer risks 6 to 8 points on his licence, plus a fine, if he tells the truth.
Norman is correct in stating that 6 to 8 points (plus a fine) is the standard penalty for driving with no insurance but this is not mandatory. If the employer is honest, your friend might receive a lower penalty.
Your friend should certainly ensure that she is represented by a solicitor. As Norman indicates, every court has a duty solicitor available, who can provide basic services free of charge. However, it might be better to contact a solicitor well before the date of the court hearing. He/she could then advise your friend about whether she ask the employer to appear in person, or whether a letter would suffice. He/she could also speak to the employer, on a formal basis, to establish just how much assistance he's prepared to give.
Chris