Я заметил, что после отдыха её ресницы выглядят длиннее, а сама она — спокойнее.

Заметил is the perfective past tense of заметить. It presents the action as a single completed event: I noticed.

So the sentence means that at one particular moment, the speaker noticed this change.

If you used замечал, that would be the imperfective and would suggest something more repeated, habitual, or process-like, such as I used to notice or I was noticing.

Also, заметил is the masculine past form. A female speaker would say заметила.

Because что introduces a subordinate clause: I noticed that...

The structure is:

• Я заметил = main clause
• что после отдыха её ресницы выглядят длиннее... = subordinate clause

In Russian, a comma is normally required before что when it means that and introduces this kind of clause.

Because the preposition после requires the genitive case.

The dictionary form is отдых, but after после it becomes отдыха:

• отдых → nominative
• после отдыха → genitive after после

This is a very common pattern in Russian:

• после работы = after work
• после урока = after the lesson
• после отдыха = after rest / after a break / after a vacation

Because свой refers back to the subject of its own clause.

In the clause её ресницы выглядят длиннее, the grammatical subject is ресницы, not она. So свои ресницы would not work naturally here.

That is why Russian uses её: it simply says that the eyelashes belong to her.

Compare:

• Она накрасила свои ресницы. = She put makeup on her own eyelashes.
  Here она is the subject, so свои works.

But in your sentence:

• Её ресницы выглядят длиннее.
  The subject is ресницы, so её is the normal choice.

Because ресницы is plural.

Russian verbs in the present tense agree with the subject in number:

• ресница выглядит = an eyelash looks
• ресницы выглядят = eyelashes look

So выглядят is simply the correct plural form of выглядеть.

Длиннее is the normal comparative form of длинный: longer.

Russian often prefers the simple comparative form:

• длинный = long
• длиннее = longer

After выглядеть, this is very natural:

• ресницы выглядят длиннее = the eyelashes look longer

The version with более is possible in some contexts, but it is usually more formal or heavier in style. Here, длиннее is the most natural choice.

In Russian, as in English, the comparison can be left implicit.

So выглядят длиннее means something like:

• look longer than before
• look longer than usual
• look longer after rest than they did earlier

Russian does not need to say the second half of the comparison if it is obvious from context.

If you wanted to make it explicit, you could say something like:

• выглядят длиннее, чем раньше = look longer than before

But in your sentence, leaving it unsaid sounds completely normal.

No. Russian comparative forms do not agree in gender, number, or case.

So the same form is used with all subjects:

• он спокойнее = he is calmer
• она спокойнее = she is calmer
• они спокойнее = they are calmer

That is why спокойнее stays the same even though она is feminine.

This is different from full adjectives like спокойный / спокойная / спокойные, which do change for gender and number.

Сама она means she herself.

It adds emphasis and contrast:

• её ресницы = her eyelashes
• а сама она = and she herself / while she herself

So the sentence is contrasting two observations:

1. her eyelashes look longer
2. she herself looks calmer

Without сама, the sentence would still be grammatical, but the contrast would be weaker.

Yes, but the emphasis would be a little different.

• сама она puts stronger focus on сама right away
• она сама is also possible, but here it sounds a bit less neatly contrastive

In this sentence, а сама она works especially well because it mirrors the contrast with её ресницы:

• её ресницы ...
• а сама она ...

So сама она is a very natural stylistic choice here.

The dash shows that something has been left out but is understood from the previous part of the sentence.

The full idea is:

• а сама она выглядит спокойнее

Since выглядит is easy to understand from the first clause, Russian often omits it and uses a dash:

• её ресницы выглядят длиннее, а сама она — спокойнее

This kind of dash is very common in Russian with parallel structure and ellipsis.

А often connects two related ideas while also showing a contrast of topic.

Here the sentence is not saying that the second part contradicts the first part. It is more like:

• her eyelashes look longer, and as for her herself, she looks calmer

So а is better than:

• и, which would sound more like simple addition
• но, which would sound like a stronger opposition

In this sentence, а gives exactly the right feeling of contrast without contradiction.