It depends upon whether the conviction is under 'Section 20' (="GBH") or 'Section 18' ("GBH with intent").
The use of a 'weapon' (such as a glass) is often sufficient to get 'with intent' added to a GBH charge. However it's likely that the offender's defence counsel will try to argue that there was actually no specific intent to cause grievous bodily harm to anyone.
If you want to read more about the legal definitions of 'GBH' and 'GBH with intent', read paragraphs 50 to 67 of this document from the Crown Prosecution Service:
http://www.cps.gov.uk...s_against_the_person/
Unless there are very exceptional circumstances (which a judge must explain in open court) judges are obliged to sentence offenders in accordance with the guidance contained in this document:
http://www.sentencing...inst-the%20person.pdf
The relevant tables are on pages 13 and 15 but it needs to be noted that those sentences refer to a first-time offender convicted after a trial. An early guilty plea can see the sentence cut by up to one third. Previous convictions (particularly for violence) can see the sentencing range moved upwards.
If the victim has not already done so, she should make a claim for compensation to CICA:
http://www.cica.gov.uk/
Chris