Why does she like being called a "good girl" and what do you all think of rewards?

I have read a few parenting books over the last few years. I remember one book saying not to call your child "good girl/boy" for doing whatever it is they did, instead to praise the "act" and their "effort" by saying "good job for doing...." or something else to that effect. Well, I have tried to follow that to the best of my ability.

However a year or so ago, I noticed that when her both her nanas say "good girl" after she does something, she gets a gleam in her eye and you can see her spirit just lifts and she loves it!
So, since I noticed that, I started occassionally saying it myself and I can see she LOVES it! I've even heard her talking to her imaginary friends later to tell them I said she was a good girl!

Now, this is my dilemma....
I don't want her to grow up with an unsaid / undue outward pressure on her to "be good" (as that is definitely not what God wants) as that is what that parenting book talked about, I don't want her self worth to be determined by how good she is but by what God thinks of her and I want her to be praised for her efforts and for doing the right thing .
So, why does she love being called a good girl?
Is it really all that bad to say it sometimes?
I am still pondering.....

The other parenting matter I am grappling with at the moment is "doing something because it's right, rather than for a reward".
I grew up in a world with no rewards for doing what I was meant to do, chores, obedience, good habits, etc etc.
Rather, it was respect for authority that motivated me and an attitude of I need to do it coz it's the right thing to do (sorry this isn't meant to be a brag:)) and hopefully it still is with me these days:)
Wind the clock forward a few years and I read about Charlotte Mason's motto for her students:
"I am, I can, I ought and I will".

My paraphrase:
I am a child of God etc...
I can do that which I need to do (because of His grace and power)
I ought to do the right thing.... and
I will do the right thing.

She also recommended no rewards other than natural consequences being the reward...eg, if I finish my lessons early I get more play time etc.
I also tend to think that other "rewards" can bring with it a sense of entitlement as one grows up..."I did this therefore I deserve this" (and how much do we see that in this generation)...which I don't want to see in her.

What CM says truly resonates with me but it's a job and a half to implement that at times !
I have taught her good habits (using Charlotte Mason's approach). But there are other habits that just don't seem to want to take root!
So, I've been pondering of late about rewards (atleast temporarily) to help get some good habits (that I am finding difficulty with) instilled in her.
Also, the Bible says God is a Rewarder so therefore He is into rewards, so are external rewards all that bad?

Or is it me that needs to have the habit of working on "instilling habits" including the habit of teaching her "I am, I can, I ought and I will". I haven't used those exact words with her (but used the method to train her) but I am thinking she's getting to the age now where she will truly be able to understand these concepts, so maybe I just need to start it?

Still pondering....and mulling things over and hope all of this is clear....what do you all think?