1. I am sure she is just fine.

2. I am sure she is only(merely)fine.
3. I am sure she is really(quite) fine.

Does #1 mean #2 or #3?

1 and 3 mean the same.

I wonder how many times Anony/rfvv is going to post about this same question. This is the third. Going to try for more?

I think Anon doesn't seem to be a native speaker.

To determine the meaning of a sentence, it is important to consider the context and surrounding words. In this case, we have three different sentences with slight variations in wording:

1. "I am sure she is just fine."
2. "I am sure she is only (merely) fine."
3. "I am sure she is really (quite) fine."

Here, each sentence introduces a different adverb ("just," "only/merely," "really/quite") that modifies the adjective "fine."

Sentence #1: "I am sure she is just fine."
The word "just" often implies simplicity, minimalism, or adequacy. In this case, it suggests that the person is confident that she is doing okay or is sufficiently fine. It does not convey any extreme positive or negative emotion.

Sentence #2: "I am sure she is only (merely) fine."
The adverb "only" or "merely" emphasizes the word "fine" to imply a lesser level of well-being. It suggests that the person believes she is not doing exceptionally well and is just barely okay.

Sentence #3: "I am sure she is really (quite) fine."
The usage of "really" or "quite" in this context enhances the adjective "fine" and indicates a higher degree of well-being. It implies that the person believes she is genuinely doing well or even exceptionally well.

Therefore, sentence #1 ("I am sure she is just fine") conveys a different meaning from sentences #2 and #3. In comparing sentences #2 and #3, they are quite similar and can be considered interchangeable in meaning, both suggesting a higher level of well-being.

Please keep in mind that this interpretation is based on the customary meaning of these words and may vary depending on the context in which they are used.