I teach in QLD so work in a different system, but here year 10 marks don't count for anything as far as uni entrance is concerned. Yr 11 and 12 are the important years. The problem with failing yr 10 is that it will make it more difficult for her to achieve high senior grades without the background knowledge. Not impossible though if she wants it badly enough.
Also, if you don't go straight to uni from high school they class you as a mature age student and entry is not reliant on high school marks anymore.

It is hard being a teenager... work on getting her attitude right. There are always alternative ways to get where you want to go, her future really isn't determined by how well she does at school.