Her marks now are basically no indication of how high an ENTER she will get - AT ALL.

The only guage you have is her work ethic and her class attendance - because ultimately it is her attitude not her previous marks, that will determine her committment to the studies she is about to undertake.

WRT to her marks in her VCE Biol - the way the ENTER score is calculated takes int account a specific number of unit marks - ie - to gain a VCE you need only to have16 (in my day) units (1 + 2 and 3 + 4) So if she has this extra subject in year 10, and still completes 6 subjects next year and 5 in year 12, she will have the pick from the BEST scores of all her units.
That's not very clear lol. Essentially, if she passes all her other subjects (attains an S) then the results from Biol may not be needed to make up the aggregate that is the ENTER score.

Sit down with her and assess which subjects she wants to do, pull oput the VCE course guide from VTAC and work out what uni course she is interested in , its pre-req's and ENTERS - remember - the higher the ENTER doesnt necessarily = better courses, arts subjects often have more emphasis on interview and portfolio to get into uni.

HTH