Mi abuela siempre ha sido muy independiente y prefiere hacer las cosas a su manera.

In modern Spanish, possessive words like mi, tu, su, nuestro usually replace the article, so you say:

• mi abuela = my grandmother
• su casa = his/her/their house

You do not normally say la mi abuela in standard modern Spanish.

Ha sido is the present perfect of ser:

• ha sido = has been

So siempre ha sido muy independiente means she has always been very independent.

This describes a quality that started in the past and is still true now.

If you said siempre es muy independiente, it sounds less natural for this idea. Spanish usually prefers siempre ha sido when talking about a lifelong characteristic that continues into the present.

These forms are different past tenses:

• ha sido = has been
  A past-to-present idea; still relevant now
• fue = was
  A completed past fact or event
• era = used to be / was
  Background description in the past

Here, siempre ha sido works best because the sentence presents independence as a continuing trait up to the present.

For example:

• Mi abuela siempre ha sido muy independiente.
  She has always been independent, and that is still true.
• Mi abuela era muy independiente.
  She was very independent; this sounds more like a past description.
• Mi abuela fue muy independiente.
  Less natural here unless talking from a clearly past perspective.

Also, in Spain, the present perfect is used quite often for past situations connected to the present.

Because independiente is an adjective ending in -e, and many Spanish adjectives ending in -e have the same form for masculine and feminine.

So you get:

• mi abuelo es independiente
• mi abuela es independiente

Only the article or noun tells you whether it is masculine or feminine.

Prefiere is the third person singular form of preferir in the present tense, because the subject is mi abuela.

Conjugation:

• yo prefiero
• tú prefieres
• él/ella/usted prefiere

This verb is also a stem-changing verb: e → ie in most present-tense forms.

So it is:

• preferir
• prefiere, not prefera or preferir

After a verb like preferir, Spanish normally uses an infinitive when the same person does both actions.

Here:

• Mi abuela prefiere hacer...
• Literally: My grandmother prefers to do...

Your grandmother is both the one who prefers and the one who does, so Spanish uses the infinitive hacer.

Compare:

• Prefiere hacer las cosas ella misma.
  She prefers to do things herself.

Literally, it means to do the things, but in natural English it usually means to do things.

It is a very common expression in Spanish:

• hacer las cosas bien = to do things properly
• hacer las cosas rápido = to do things quickly
• hacer las cosas a su manera = to do things her way

So here las cosas is a general phrase meaning things, tasks, or the way things are done.

Spanish often uses the definite article in places where English would not.

So hacer las cosas is a very natural Spanish expression, even though English usually just says do things.

This is one of those places where Spanish sounds more idiomatic with the article.

A su manera means in her own way or her way.

It is an idiomatic expression:

• a mi manera = my way
• a tu manera = your way
• a su manera = his/her/their way

So:

• prefiere hacer las cosas a su manera
  = she prefers to do things her own way

It suggests personal independence, habits, or not wanting others to interfere.

Because the fixed expression is a su manera.

Spanish uses a in this idiom to express in the manner/style of someone:

• a mi manera
• a tu manera
• a su manera

Using de su manera would not sound natural here.

A similar expression is a su modo, which also means in his/her own way.

Yes, su can mean:

• his
• her
• its
• their
• your (formal singular)

So by itself, su manera is grammatically ambiguous.

But in this sentence, the context makes it clear that su refers to mi abuela, so it means her way.

If you ever need to make it clearer, Spanish can add:

• la manera de ella

But that is usually unnecessary here.

Because the subject is the same for both verbs:

• Mi abuela siempre ha sido muy independiente
• y (mi abuela) prefiere hacer las cosas a su manera

Spanish often leaves out repeated subjects when they are already clear.

You could repeat it for emphasis, but it is not necessary:

• Mi abuela siempre ha sido muy independiente y mi abuela prefiere...

That sounds repetitive unless you really want emphasis.

A useful way is to split it into two parts joined by y:

1. Mi abuela siempre ha sido muy independiente
   Subject + time word + present perfect + adjective

2. y prefiere hacer las cosas a su manera
   and + present tense verb + infinitive phrase + idiomatic expression

So the full structure is:

• Mi abuela = subject
• siempre ha sido = has always been
• muy independiente = very independent
• y = and
• prefiere = prefers
• hacer las cosas = to do things
• a su manera = her own way

Yes, you could, and it is grammatical.

The difference is nuance:

• es muy independiente = she is very independent
  A present description
• siempre ha sido muy independiente = she has always been very independent
  A lifelong or long-term characteristic

The original sentence is stronger because it shows that this is not just true now; it has been true for a long time.

Yes. It is completely natural in Spain.

One especially notable point is siempre ha sido, because speakers in Spain often use the present perfect in situations that are strongly connected to the present.

In some Latin American varieties, you might also hear other past forms more often in similar contexts, but the original sentence is very standard and natural for Spain.