I'd look away give it thought then look her in her eyes and say "chemistry."
From there I would continue based off her response and intent
Is she going to try to pry and qualify?
Is she going to pry then disqualify?
Is she trying to sus out my position as a lover or boyfriend?
Is she bringing this up early in the convo or in an isolated spot where maybe talking shouldn't be happening (escalation window)?
Before or after a man and woman frame established/escalation?
What compliance have I gained or she showcased? Her asking this first isolation is different than her asking this after we've made out. Different feelings of investment and intent.
In this question I have no idea the context or stage, but my safety ambiguous response would be
"Chemistry" paired with tight eye contact and if possible use this thread to close proximity.
Many fun, sensual, delightful things you can get into when discussing chemistry.
So open too that if she tries to disqualify before pinning you down she's just being a brat, but if she disqualifies after you go into what that means or looks like to you...might have some room to consider if you'd like to continue the set.
Never had a woman disqualify it though. Even allowed me to get sexual as if there is chemistry present many women have agreed with me...the timescale, rules, etc doesn't matter provided comfort, trust, and openness is present.
Then you can explore that chemistry together at whatever pace works
after she eats that up