Она сказала, что я не виноват, и мне стало легче.

Because the subject is она. In the Russian past tense, verbs agree with the subject in gender and number:

• он сказал = he said
• она сказала = she said
• оно сказало = it said
• они сказали = they said

So сказала tells you the speaker is talking about a female person.

Сказала comes from сказать, which is usually perfective. It presents the action as a single completed act: she said it, and that moment is treated as finished.

Говорила comes from говорить, which is imperfective. It usually means something more like:

• she was speaking
• she used to say
• she was telling

In this sentence, the point is that she said one specific thing, so сказала is the natural choice.

Here что means that and introduces the content of what she said:

• Она сказала, что... = She said that...

In English, that is often optional: She said I wasn’t to blame. In Russian, что is normally kept in this kind of sentence.

Because виноват is the normal predicative form here.

In Russian, many adjectives have a short form that is often used after to be or in statements like X is Y. That is what you see here:

• Я виноват. = I am to blame.
• Я не виноват. = I am not to blame.

Виноватый is the full form and is more natural when directly describing a noun:

• виноватый человек = a guilty / at-fault person

So in this sentence, я не виноват is the standard, natural phrasing.

Because виноват agrees with the person referred to by я, not with она.

In Russian, я does not show gender by itself, so the adjective tells you the speaker is male:

• я не виноват = I am not to blame (male speaker)
• я не виновата = I am not to blame (female speaker)

So this sentence strongly suggests that the person saying я is male. If the speaker were female, the sentence would be:

Она сказала, что я не виновата, и мне стало легче.

Because Russian often expresses feelings and states with the experiencer in the dative case.

So instead of saying something literally like I became better, Russian often says something more like:

• мне холодно = I am cold
• мне грустно = I am sad
• мне стало легче = I felt better / it became easier for me

Here мне is the dative form of я. It means to me / for me, and that is the normal structure in Russian for this kind of feeling or change of state.

Because this is an impersonal construction.

There is no normal grammatical subject here. Russian often uses neuter singular past tense in impersonal sentences:

• стало холодно = it got cold
• было трудно = it was difficult
• мне стало легче = I felt better / it became easier for me

So стало does not agree with мне. It is just the standard neuter singular form used in this kind of impersonal expression.

Легче is the comparative form, meaning easier, lighter, or in context better / more relieved.

So:

• мне стало легче literally means it became easier/lighter for me
• natural English: I felt better or I felt relieved

If you said мне стало легко, that would sound more like it became easy for me, which is possible in some contexts but is not the usual way to express emotional relief after hearing something reassuring.

It can mean either, depending on context.

In everyday speech, я не виноват very often means:

• It’s not my fault
• I’m not to blame

In a more legal or serious context, it can also mean:

• I’m not guilty

So the basic idea is that the speaker bears no blame or responsibility. The exact English translation depends on the situation.

There are two reasons.

First, Russian normally puts a comma before что when it introduces a subordinate clause:

• Она сказала, что я не виноват

Second, there is a comma before и because it joins two clauses with separate predicates:

• Она сказала...
• мне стало легче

So the structure is:

• main clause: Она сказала
• subordinate clause: что я не виноват
• second clause: и мне стало легче

That is why the punctuation is correct.

Yes. Russian word order is flexible, though the version you have is neutral and very natural.

This sentence sounds standard:

Она сказала, что я не виноват, и мне стало легче.

You could also hear variations for emphasis, such as moving мне or changing the rhythm, but the original is the most straightforward.

A useful thing to notice is that мне стало легче already has a very common, natural order in Russian: dative experiencer first, then the impersonal verb phrase.

So while Russian word order can change, this version is a good one to learn as the default.