I was intending to write more on this and issues relating to VBAC. Instead I will refer to two posts written on Birthrights and Mental Health and Capacity Law which explain the situation well. I will also refer to the following comments by AIMS.
The decision to have a Vaginal Birth after Caesarean (VBAC) had been a huge issue in our postbag and maternity care for a long time, and is very much associated with women's desire for control, and also their mental health. Originally the obstetricians policy was "once a caesarean, always a caesarean" and it was women themselves - particularly here, but also in the US - who wanted a chance to have a normal birth and many opted out of hospital care in this country to have home births, with private midwives or even no care, because they were pushed into having CS in hospital. (of course this is not all women's choice - but we support their right to choose whatever it may be) Finally both the ACOG in the States and the RCOG and department of Health here has come out supporting VBACs. One of the reasons for the professional's volte face was the number of women with previous sections who had an embedded placenta as a result of the previous operation, and removal of this (depending on degree of penetration of the uterine wall) can lead to massive, and sometimes fatal, haemorrhage. Having to deal with a few of these in theatre (plus maternal deaths) encouraged them to listen to what women wanted, which proved actually to be safer. Here are RCOG current guidelines http://www.rcog.org.uk/womens-health/clinical-guidance/birth-after-previous-caesarean-birth-green-top-45
I think it is crucial for her lawyer to get the medical advice that Mostyn had, so that it is possible to see if it was balanced. We do not know if a balanced picture of risks was provided. The risk of what is called "rupture" but in fact is much more likely to be "dehiscence" (gradual and partial separation of the scar, which can be monitored for and a quick CS can then be done) is in fact a very small one, and in most cases of course, risks are explained to women and she chooses between options
Here is the NICE guideline on Caesarean which would have been in place at the time. Please note section on Woman Centred Care