Hon vill bara vara sig själv.

Because the subject and the object refer to the same person.

In Swedish, when she does something that refers back to herself, you normally use the reflexive pronoun sig in the third person:

• hon ... sig = she ... herself
• han ... sig = he ... himself
• de ... sig = they ... themselves

So:

• Hon vill vara sig själv = She wants to be herself.

If you said henne själv, that would usually sound non-standard or emphatic in a different way. In normal Swedish, sig själv is the expected form here.

Sig själv means herself / himself / itself / themselves, depending on who the subject is.

In this sentence, it means herself because the subject is hon.

A very useful pattern is:

• vara mig själv = be myself
• vara dig själv = be yourself
• vara sig själv = be himself/herself/itself
• vara oss själva = be ourselves
• vara er själva = be yourselves
• vara sig själva = be themselves

So Hon vill bara vara sig själv uses a very common Swedish expression: vara sig själv = be oneself / be yourself / be herself, depending on the subject.

Because sig alone does not work naturally here.

In Swedish, the idiomatic expression is vara sig själv. The word själv is what gives the sense of self in herself.

Compare:

• sig = herself/himself as an object in many situations
• sig själv = herself/himself in the stronger sense of one’s own self

So:

• Hon ser sig i spegeln = She sees herself in the mirror.
• Hon vill vara sig själv = She wants to be herself.

You cannot normally say Hon vill vara sig for this meaning.

No, they are different.

• vara sig själv = be oneself, be your true/natural self
• vara själv = be alone, be by yourself

Examples:

• Hon vill vara sig själv. = She wants to be herself.
• Hon vill vara själv. = She wants to be alone.

This is a very important distinction, because English learners often confuse these.

Because vill is a modal verb, and modal verbs in Swedish are usually followed directly by the infinitive.

So:

• hon vill vara = she wants to be
• jag kan komma = I can come
• du måste gå = you must go

Not:

• hon vill att vara

So the pattern is:

• subject + vill + infinitive

Here:

• Hon vill bara vara sig själv.

Here bara means just / only, and it modifies the verbal idea vara sig själv.

So:

• Hon vill bara vara sig själv = She just wants to be herself.

This is the most natural placement in a neutral sentence.

Swedish often places words like bara before the infinitive when they belong with it:

• Jag vill bara hjälpa. = I just want to help.
• Vi försöker bara förstå. = We’re just trying to understand.

If you move bara, the emphasis can change.

Sometimes yes, but the meaning or emphasis changes.

The neutral version is:

• Hon vill bara vara sig själv.

Other placements may sound marked, contrastive, or less natural in ordinary speech.

For example:

• Bara hon vill vara sig själv does not mean the same thing. It means something more like If only she wants to be herself or Only she wants to be herself, depending on context.
• Hon bara vill vara sig själv is possible in speech, but gives a different rhythm/emphasis.
• Hon vill vara sig själv bara can sound colloquial and usually needs context.

So for learners, Hon vill bara vara sig själv is the best standard model.

The structure is:

• Hon = subject
• vill = finite verb
• bara = adverb
• vara = infinitive
• sig själv = reflexive expression

So the sentence is:

• Subject + finite verb + adverb + infinitive + object/complement

This also fits the normal Swedish main-clause pattern where the finite verb comes early in the sentence.

The reflexive part changes depending on the subject.

Examples:

• Jag vill bara vara mig själv. = I just want to be myself.
• Du vill bara vara dig själv. = You just want to be yourself.
• Han vill bara vara sig själv. = He just wants to be himself.
• Hon vill bara vara sig själv. = She just wants to be herself.
• Vi vill bara vara oss själva. = We just want to be ourselves.
• Ni vill bara vara er själva. = You just want to be yourselves.
• De vill bara vara sig själva. = They just want to be themselves.

Notice that plural forms use själva:

• oss själva
• er själva
• sig själva

Because själv changes form depending mainly on singular vs. plural, and sometimes grammatical gender.

In this sentence, the subject is one person:

• hon → sig själv

With plural subjects, you usually get själva:

• Vi vill vara oss själva.
• De vill vara sig själva.

So here själv is correct because it refers to one person.

Usually it is about identity, authenticity, or behaving naturally.

Vara sig själv often means:

• be your real self
• act naturally
• not pretend to be someone else
• not change yourself to please others

So Hon vill bara vara sig själv often carries an emotional or personal meaning, not a literal physical one.

It usually does not mean that she wants to be alone. For that, Swedish would more naturally use vara själv or vara ensam, depending on context.