Taking away Tifa's materia, best equipment, blah blah, you're still left with her limit break abilities.

Cammy is supposed to be a genetically altered super soldier and habitually takes on and defeats warriors of superior Ki strength with nothing more than her agility, respectable strength, fighting instinct, and good ol' CQC.

I think a leveled up Tifa with no unnatural ability enhancers vs. a government weapon like Cammy would be pretty even.