Have you considered taking lessons yourself? Otherwise I'd just invest in a pair of good headphones, or convince your parents to pay for some extracurricular activity. Or do your homework outdoors!
Why don't you negotiate a time table? Instead of 2-3 hours straight she gives you 1 hour of silence in between so its not as intense. Maybe ask her to only start her classes an hour after you get home from skool?
I think the solution to this problem you're facing is RAPE
RAPE
RAPE
RAPE
RAPERAPERAPERAPERAPERAPERAPERAPERAPE