I also give a key to my maid. Because it is very inconveient if she doesn't have the key, especially during the emergence case. If you don't trust her, you can consider Ibb's suggestion. I think this is a good idea.
I will give the key to her when my son go to playgroup.
我鐘意你同我講 I Love U, I Love U Too!
You are the sunshine of my life. That's why I'll always stay around. You are the apple of my eye. Forever you'll stay in my heart.
the best is no keys to them:
1. actually they stay indoor,
2. this make them alart you are NOT TOTALLY depending on them.
3. at least you can sure keys are not duplicated in their society.
4. key for gate or key for door only, not the whole set, you should have your last defence.