don't know the definitive answer but I think your friend needs to seek more information herself.
Having a child with down syndrome is not the end of the world - instead the beginning of a whole new world. I have a 4yo with down syndrome and have gone on to have another dd and am expecting my third.
My chance of having another child with down syndrome at this stage was 1 in 58 - rather a higher chance than your friend. With my second pregnancy it was around that as well.
I never had a CVS or amnio with my three pregnancies. Dd1 - hard marker of a heart defect that placed my chance around the 1 in 5 - anomaly scans showed definite characteristics of a child with down syndrome. Why did we not have an amnio or CVS _ because to us - it would not make a difference. This was our baby and she was going to be born. Having said that - we had friends who had children with down syndrome and it wasn't something to be so fearful of - despite the views of a number of medical professionals.
A high risk nuchal translucency result can be related to more conditions than down syndrome - which unfortunately is something that most medical professionals forget to tell women.
That phrase 'having a downs' is incredibly upsetting - you are having a child - first and foremost who may happen to have down syndrome. The biggest thing I have learnt since having my daughter - is how like other 4yo she is rather than how different.
Unfortunately having invasive testing such as CVS and amnio do carry a chance of miscarriage and I guess for your friend she has to weigh up that chance against her chance of having a child with some condition.
I would say if your friend is adamant she will not have a child with down syndrome then go ahead and have the CVS and she can then do what she wishes with the further information. If it makes no difference then I do not see the point of putting yourself through such invasive testing - just how I feel about this.
I do think she needs to seek more information regarding down syndrome before she makes such a life changing decision ( either way). It appears she does not have a real view of children with down syndrome.
Unfortunately the only information I have regarding amnios and CVS is that of the babies that are miscarried after the testing - 3/4 of those children have no conditions and are in fact NT.
DSA UK website this might be a good starting point.