Ella, por su parte, llamó ayer.

Yes. In Spanish, subject pronouns are often omitted because the verb ending already shows who the subject is.

So llamó ayer already means she/he called yesterday, depending on context.

Here, ella is included for a reason, usually to:

• add contrast
• emphasize who did the action
• help make the reference clearer in context

In this sentence, that fits especially well because of por su parte, which often sets one person in contrast with another. So Ella, por su parte... is like saying:

• She, for her part, called yesterday
• As for her, she called yesterday
• She, on the other hand, called yesterday

So ella is not grammatically necessary, but it is very natural if the speaker wants emphasis or contrast.

Por su parte is an expression that often means something like:

• for her part
• as for her
• on her side
• meanwhile, she
• she, in turn

It usually introduces what that person did or thought, often in contrast with someone else already mentioned.

For example:

• Juan no respondió. Ella, por su parte, llamó ayer.
  • Juan didn’t reply. She, for her part, called yesterday.

So the phrase does not literally mean a physical part here. It is an idiomatic way to show that we are now talking about that person’s own action or role in the situation.

Because por su parte is being used as a parenthetical or inserted expression. It interrupts the main structure of the sentence rather than being essential to it.

The core sentence is:

• Ella llamó ayer.

Then por su parte is inserted to add a nuance of contrast or perspective:

• Ella, por su parte, llamó ayer.

The commas show that this phrase is extra information, similar to how English might write:

• She, for her part, called yesterday.

Without commas, the sentence would feel less standard in this use.

Yes. That is perfectly possible.

Spanish word order is flexible, especially with discourse phrases like por su parte. These are all possible, though they may sound slightly different in emphasis:

• Ella, por su parte, llamó ayer.
• Por su parte, ella llamó ayer.
• Ella llamó ayer, por su parte. (less common in many contexts)

Putting por su parte first can make the contrast even more prominent, as if you are setting up as for her...

Llamó is the preterite form, and llamaba is the imperfect. They express different kinds of past actions.

• llamó = she called
  This presents the action as a completed event.

• llamaba = she was calling / she used to call
  This gives a background, repeated, or ongoing sense.

Since ayer means yesterday, a completed time period, the preterite llamó is the normal choice:

• Ella llamó ayer = She called yesterday

If you said llamaba ayer, it would usually need more context and would sound like an ongoing past action, for example:

• Ayer llamaba cuando se cortó la luz.
  • Yesterday she was calling when the power went out.

So in this sentence, llamó is the expected tense.

The accent mark distinguishes llamó from llamo.

• llamó = he/she called or you called (preterite)
• llamo = I call (present tense)

So the accent is important because it changes both the pronunciation and the meaning.

Compare:

• Yo llamo = I call / I am calling
• Ella llamó = She called

In pronunciation, llamó is stressed on the last syllable: lla-MÓ.

Usually, yes.

In modern everyday Spanish, llamar commonly means to call someone, especially by phone.

So:

• Ella llamó ayer usually means She called yesterday

In Spain, this is a very standard way to talk about phone calls.

Of course, llamar can also mean to call out, to call someone by a name, or to summon, depending on context. But with ayer and no object, most learners should understand it here as made a phone call / phoned.

Yes, if the context makes it clear who she is.

Spanish often leaves out the subject pronoun, so:

• Por su parte, llamó ayer

can be perfectly natural if we already know the subject is she.

However, there is a small issue: llamó could also mean he called or you called (usted) depending on context. So including ella helps remove ambiguity and strengthens the contrast.

That is why Ella, por su parte, llamó ayer may sound especially appropriate if the speaker wants to be clear and contrastive.

Yes, ayer can move around.

All of these are possible:

• Ella llamó ayer.
• Ayer llamó ella.
• Ella ayer llamó.
• Ella llamó ayer.

The most neutral and natural version in many cases is to put ayer at the end.

Changing the position can change the emphasis:

• Ayer llamó ella may emphasize yesterday
• Ella ayer llamó can sound more marked or literary depending on context

So in your sentence, ayer at the end is just a normal, neutral placement.

Yes, but it is a little more formal or structured than very casual conversation.

You will often see or hear it in:

• news
• formal speech
• narration
• written Spanish
• explanations comparing different people’s actions

In very casual speech, people might use other ways to express a similar idea, depending on context, such as:

• ella, en cambio... = she, on the other hand...
• en su caso... = in her case...
• pues ella... = well, she...

So por su parte is common and useful, but it can sound slightly more polished than the most everyday spoken alternatives.

They can both express contrast, but they are not exactly the same.

Por su parte focuses on that person’s own role, action, or position:

• Ella, por su parte, llamó ayer.
  • As for her / for her part, she called yesterday.

En cambio means more directly by contrast / on the other hand / instead:

• Ella, en cambio, llamó ayer.
  • She, on the other hand, called yesterday.

So:

• por su parte = highlights what that person did from their side
• en cambio = highlights stronger contrast between two situations

Sometimes both work, but the nuance is slightly different.

In theory, yes: su can mean his, her, your, their, or its, depending on context.

But in this sentence, because we have Ella, por su parte..., the natural interpretation is that su refers to ella.

So here:

• Ella, por su parte... = She, for her part...

The subject right before the phrase makes the reference clear.

It would also work in Latin America.

Nothing in Ella, por su parte, llamó ayer is uniquely Peninsular Spanish. It is standard Spanish and widely understood across the Spanish-speaking world.

The verb llamar for to call is also common in both Spain and Latin America. So this sentence is not particularly region-specific.