Desde que vive sola, mi prima se ha vuelto más independiente y más segura de sí misma.

Desde que means since in a time sense: from the time that.

So Desde que vive sola means Since she has been living alone or Ever since she started living alone.

It introduces the starting point of a situation that has led to a change:

• Desde que vive sola, ... = Since she lives alone / Since she started living alone, ...

A very common learner mistake is to confuse desde and desde que:

• desde
  • noun/time expression: desde 2020, desde marzo
• desde que
  • verb: desde que vive sola

In Spanish, after desde que, the present tense is often used when the situation started in the past and is still true now.

So:

• Desde que vive sola = Since she has been living alone / since she started living alone and still does

Spanish often uses the present where English prefers a present perfect or present perfect continuous.

Compare:

• Desde que trabaja aquí, está más contento. = Since he started working here / Since he has been working here, he is happier.

If the situation were finished, another tense could appear, but here vive shows that she still lives alone now.

Because sola agrees with the person it describes, and that person is feminine: mi prima.

• masculine singular: solo
• feminine singular: sola
• masculine plural: solos
• feminine plural: solas

So:

• Mi primo vive solo.
• Mi prima vive sola.

Here sola means alone / by herself, not lonely.

It means she lives alone.

That is an important distinction:

• vivir solo/a = to live alone
• sentirse solo/a = to feel lonely

So:

• Mi prima vive sola. = She lives alone.
• Mi prima se siente sola. = She feels lonely.

English learners sometimes connect solo/a only with emotion, but in Spanish it can simply describe being physically by oneself.

The verb is volverse, which means to become in this kind of sentence.

So:

• volverse = to become, to turn into, to grow/change into

In the present perfect:

• se ha vuelto = has become

The se is not optional here, because volverse is the standard form of the verb with this meaning.

Compare:

• Se ha vuelto más independiente. = She has become more independent.
• Ha vuelto. = She has returned.

Without se, volver usually means to return or to turn something depending on context, so se changes the meaning a lot.

Because the sentence talks about a change over time, not just a state.

• es independiente = she is independent
• está segura de sí misma = she feels/is self-confident at the moment
• se ha vuelto independiente = she has become independent

Volverse emphasizes transformation:

• before, she was less independent
• now, as a result of living alone, she has changed

So se ha vuelto is a very natural choice when you want to express has become.

Because volver is an irregular past participle verb form? Actually, no: volver has the regular participle vuelto, not volvido.

Its past participle is:

• volver → vuelto

So:

• ha vuelto
• se ha vuelto

Some common participles are irregular and must simply be learned:

• hacer → hecho
• decir → dicho
• ver → visto
• poner → puesto
• volver → vuelto

Se ha vuelto is the pretérito perfecto: has become.

In Spain, this tense is very common for changes or events connected to the present. Here, the idea is:

• she started living alone in the past
• that has affected her up to now
• now she is more independent and confident

So se ha vuelto fits very well because the change is relevant now.

In some varieties of Spanish, especially in much of Latin America, a simple past might also be common in some contexts:

• se volvió But in Spain, se ha vuelto sounds very natural here.

Yes, you could say:

• más independiente y segura de sí misma

That is grammatical and natural.

But repeating más:

• más independiente y más segura de sí misma

makes both qualities feel a bit more clearly balanced or emphasized.

So the difference is mostly stylistic:

• más independiente y segura = slightly more compact
• más independiente y más segura = slightly more explicit/emphatic

It means self-confident, literally something like sure of herself.

Breakdown:

• segura = sure, confident
• de sí misma = of herself

So:

• ser/estar seguro/a de sí mismo/a = to be self-confident / to be sure of oneself

Examples:

• Es una chica muy segura de sí misma. = She is a very self-confident girl.
• No está seguro de sí mismo. = He is not confident in himself.

Here it means emotional or personal confidence, not physical safety.

Because sí mismo/a is the reflexive form used when the person referred to is the same as the subject of the clause.

Here, the subject is mi prima, and the confidence refers back to mi prima herself:

• mi prima ... segura de sí misma

So sí misma is the natural reflexive form.

Compare:

• María habla de sí misma. = María talks about herself.
• María habla de ella. = María talks about her. (usually another woman, or ambiguous in some contexts)

In this sentence, sí misma clearly shows that the confidence is in herself.

Because it agrees with the person it refers to, which is feminine singular: mi prima.

Forms:

• sí mismo = himself / oneself (masculine)
• sí misma = herself / oneself (feminine)
• sí mismos
• sí mismas

So:

• Mi primo está seguro de sí mismo.
• Mi prima está segura de sí misma.

Notice that both segura and misma agree with mi prima.

Yes. Mi prima means my female cousin.

Spanish distinguishes:

• primo = male cousin
• prima = female cousin

English usually just says my cousin, unless the gender matters and you choose to make it explicit in some other way.

So in translation:

• mi prima = my cousin
• or, if needed for clarity, my female cousin

Yes, there can be a difference.

In this sentence, independiente is the most natural word for personal independence:

• able to manage her own life
• less dependent on others

Autónoma can sometimes work, but it often sounds a bit more formal, abstract, or linked to functioning on one’s own in a practical sense.

So:

• más independiente = very natural here
• más autónoma = possible in some contexts, but less neutral for everyday personal development

For a cousin becoming more mature from living alone, independiente is the best fit.

Yes, you could say:

• Mi prima se ha vuelto más independiente y más segura de sí misma desde que vive sola.

That is grammatical and natural.

Putting Desde que vive sola at the beginning helps frame the cause or time reference first. It gives a slight emphasis to the idea that living alone is what triggered the change.

So both are correct:

• Desde que vive sola, mi prima...
• Mi prima... desde que vive sola.

The first version is often a bit smoother when setting the context before the main statement.