Both are nearly the same to me.
The nuances are about perspective:
The sentence that uses "she" is talking about the "the little girl" from the memory, almost as if she was a different person than the woman in the present.
You can use that phrasing to distance the two people.
This is especially common when the speaker's view of the person has changed: Before we started hanging out, I only knew you as the guy who came late to class everyday because he kept oversleeping.
The sentence that uses "you" links the person in the memory with the actual person.
There is no distancing.
ell.stackexchange.com/users/26135/Senjougahara Hitagi
Both are correct.
In the first sentence, the speaker remembers the girl with particular label.
The label being "a little-girl-who-over waters-plants-because-she-doesn't-know-when-to-stop-giving.".
In the second sentence, the speaker is directly telling her that he remembers her as a little girl who over waters her plants.
You can use both as neither is incorrect.
It is just the matter of the way you address the subject.
ell.stackexchange.com/users/27122/Varun Nair
The key part of the sentence that you've not picked up on is the 'as'.
The writer is making a comparison between 'you' and 'a little girl who overwaters plants because she doesn't know when to stop giving'.
ell.stackexchange.com/users/27367/AdamJS
We can assume that the addressed audience of this sentence is an adult woman.
From one perspective, the adult woman and the little girl are the same person.
From another, they are not.
The little girl no longer exists and is not the same as the adult she later became.
I have no reason to suspect, for instance, that this woman over-waters her plants.
The model sentence assumes this second perspective.
The woman is represented by a second-person pronoun: "you".
The phrase "a little girl" is a third-person noun phrase.
The antecedent of "she" is "a little girl", making the third-person pronoun form appropriate.
The little girl isn't even real.
She's a product of the speaker's imagination or memory, nothing more than some hypothetical figment.
She might never have existed at all, outside of the speaker's perceptions.
We can treat her as an eternal concept.
As an eternal concept, that it agrees with a verb the present tense makes sense.
In the speaker's memory, the little girl still doesn't know when to stop.
Your proposed revision takes the other perspective.
The woman and the little girl are the same person, but at different stages of her life.
The "you" of "you didn't know when to stop giving" has the same antecedent as the "you" earlier in the sentence.
Both refer to the addressed adult woman.
Your revision uses the past tense.
This is sensible because that stage of development is in the adult woman's past.
The "you" and the "she" exist in different timeframes.
These different timeframes lead to different implications.
Your revision implies that the woman now knows when to stop.
She didn't know as a child, but the past tense lets us safely assume that she has stopped not knowing.
The difference between the woman and the child is established.
A different revision uses the present tense throughout:
I still remember you as a little girl who over-waters plants because you don't know when to stop giving.
This implies that nothing has changed.
The woman didn't know when to stop as a child, and she doesn't know when to stop as an adult.
The similarity between the woman and the child is established.
In the original, the third-person "she" is conceptually distinct from the second person "you".
The little girl eternally lacks that knowledge.
From that sentence, we have no idea at all whether the adult woman knows.
The original sentence gives me no reason to assume that the adult woman over-waters her plants, but it also gives me no reason to assume that the present-day woman doesn't over-water her plants.
The difference or similarity between woman and child is left unspecified.
That lack of specificity is not possible with the pronoun "you", but it is possible with the pronoun
"she".
That's the difference that a shift in perspective can produce.
ell.stackexchange.com/users/12283/Gary Botnovcan
The first sentence means: I still remember you as X. where the adjective-phrase X stands for "a little girl who over-waters plants because she doesn't know when to stop giving".
The second sentence means: I still remember you as Y because you didn't know when to stop giving.
where the adjective-phrase Y stands for "a little girl who over-waters plants".
There is a difference in the adjective-phrases.
As another example, consider: You have the same color as the tail of the horse that is white.
The second form of the sentence would not make much sense here.
ell.stackexchange.com/users/27379/user1952500
I read this somewhere and it said:   I still remember you as a little girl who overwaters plants because  she  doesn't know when to stop giving.   But in this sentence, the person says 'you' and 'little girl', but then uses 'she' as a third person.   Shouldn't it be:   I still remember you as a little girl who overwaters plants because  you  didn't know when to stop giving.
Using she or you to refer to someone "as a little girl"
ell.stackexchange.com
<pronouns>
ell.stackexchange.com/questions/75125
ell.stackexchange.com/users/27354/Rohan Arora
Both are correct. In the first sentence, the speaker remembers the person. In the second sentence, the speaker is   directly  telling her that he remembers her as a little girl who over waters her plants. The sentence that uses "she" is talking about the "the little girl" from a memory, almost as if she was a different person than the woman in the present. Both make sense, it is a matter of perspective.
Both make sense, it is a matter of perspective.