You should be guided by what she wants, tbh. IF she wants to learn a stringed instrument, that's a good start. Violin is a complex instrument to learn, and takes a lot of practice just to get the basics, so she has to want to do it, and has to put in the hours of practice (30 mins a day at age 8, really).
Does she have a good ear for pitch? If you don't have an ear for hearing fine details of tuning, it won't sound nice even after many years of tuition and many hundreds of hours of practice. I know some dc like this, and tbh don't understand why their parents haven't encouraged them towards an instrument with fixed pitch, like a clarinet, where being able to hear the intonation is less crucial.
You should also bear in mind that many children start learning the violin very young, and if they are moderately talented and have practised regularly, they will be pretty good by age 8. If your dd is only just starting out, she will have a lot of catching up to do, and in any ensemble situations she is likely to be sitting at the back of the 3rd violins for a long time.
If you are thinking in terms of which instrument is 'useful' in an orchestra, you might be better encouraging her towards one of the less common wind instruments - even an averagely competent bassoonist for eg. will be welcomed with open arms in most orchestras.