How do you reprimand your baby and help them understand “no” ?

Firstly, she has no impulse control at all at this age. It doesn’t start developing til later in toddlerhood. She also doesn’t know what the word “no” means. She can’t test limits because she doesn’t know there’s things she shouldn’t do.
She looks at you and waits for a reaction because she likes when you react. Any reaction you give is interesting to her. She just likes to look at you.

My 16month old love to say no at everything but when I say it to her she gets upset and has a tantrum

Babies can from 6 months understand tone of voice, facial expressions and approval/disapproval. They usually only understand “no” and boundaries and routines around 12 months. To help with what you’re dealing with the best methods would usually be to just move dangerous items away, redirect their attention and physically guide them away. I know what you mean about how it seems like they know what they’re doing is wrong as my little one is the same but I think it’s more that they get excited from your reaction to them as it’s usually “bigger” x

I get that she seems mischievous tho lol but really she probably just is happy being around you and that’s why she smiles and giggles when you tell her no

You don’t. You make the environment safe so that she doesn’t have access to anything dangerous.

Rather than saying no as she won’t understand this early, I would just redirect her and stay consistent x

You try your best to patiently redirect until they get closer to being 5-7 years old. Lmfaooo

Little babies, even three year olds, dont really fully grasp the concept of “no” they understand tone for sure, but a baby / kids brain doesn’t hear “no” as a direction, its basically just a filler word.

In our house we say “keep that in your hands” instead of “do not throw that”
“Get down safely” instead of “do not jump”