Suck it up and break it off. It’s never pleasant. It’s never easy. It’s ALWAYS messy. One or both people will always get hurt. That’s why break ups suck.
But it’ll suck even more if you wait and lead her on. Would YOU want someone to stay in a relationship with you if they weren’t into it anymore? Think about role reversal. What would you want if the roles were reversed?
Rip off the band aid.