I'm even later to the party than Sherry.
You've been lucky - no harm done - and hopefully your heart rate is getting back down to somewhere near normal now.
Take a moment, give Nala a hug, then work out a plan for *bengal* kitten proofing your home and ensuring that the cleaner is on board for keeping your kittens inside.
A little story- I live in an apartment, I planned, measured and checked, bought a load of window catches and then realised that they wouldn't hold against an adult cat. I started again with different catches, measured, checked, measured again and fitted them. One night I couldn't find Ada anywhere. Then I went into the kitchen - she was jumping up at the waist-high window on a narrow balcony, 12 floors up to get my attention.
Kittens really can get through the smallest of gaps.