You probably mean IRL, not fictional, but the 1999 Sarah Michelle Gellar vs Eliza Dushku fight to the death on the Graduation Day episode of Buffy the Vampire slayer went from commercial break to commercial break, meaning it was the longest an uninterrupted TV fight could possibly go.
Why it's a great fight:
1. Very back and forth fight not
2. Even incorporates a set of handcuffs, so the sexual implications are undeniable.
3. Both girls are in leather....
4. .....with their hair down....
5. ....and are fighting over a boy.
6. Takes place in Faith's bedroom (see #2).
7. Buffy is there to kill Faith.
8. Stunt doubles were used, but they were women.
