Sorry I know you quoted Ronandannette, but I will still give my two cents. I think that you, as her mom, have no way of knowing if a customer has or has not received good service. That is up to each customer to decide. And tipping is still discretionary so if someone chooses to tip extremely low, well, that is their money and that is the chance you take by working in a tipped position. I have no doubt that if your daughter is a good server, the few low tippers are more than made up for by the people who feel obligated to tip 25% or something.
To me, this "expected" tipping for the bare minimum was the vanguard of entitlement culture. If I give you cash and you are not happy with the amount of cash I have given you, please feel free to return my cash to me.