if she basicly tailors her list to whatever you bring. even without knowing it in advance, I wish you good luck. I agree with Ntaw, emperors fist and skyhammer would be a nice split of strengths.
and yeah Tau are in the top of best armies.
for future reference I advice to avoid such opponents. sucks the fun out of the game. also sounds like she might not handle losing well. wich makes it even less fun.