Can you remove a spell counter to activate an ability during battle?
Can she do that?


No. As Breaker's effect is not quick-play.

His effect is Speed 1, which means it can only be activated during the owner's Main Phases.

In Yugioh there are 3 speeds of effects:


Speed 1: As indicated before, can be activated during the owner's Main Phases. You can't activate a Speed 1 effect in response to any activation or condition.
Speed 2: These can be activated technically anytime, and can be chained in response to Speed 1 or Speed 2 effects (unless otherwise restricted). In spell cards these are the ones with the lightning symbol, or trap cards without any symbol for example (there are others, of course).
Speed 3: These are exclusive for Counter Trap Cards (the ones with the arrow symbol). These can be activated in response to any spell speed, and only a Counter can be activated in response to another.


So, no. Breaker can't do that as it is Speed 1 effect.