Hún er ekki vön að borða kjúkling á kvöldin, svo hún velur frekar núðlur.

Because vön agrees with hún, which is feminine singular.

The adjective is vanur = accustomed / used to, and it changes form depending on gender, number, and case:

• vanur = masculine singular
• vön = feminine singular
• vant = neuter singular

So:

• Hann er vanur ... = He is used to ...
• Hún er vön ... = She is used to ...
• Það er vant ... = It is used to ... (less common in this exact meaning)

In your sentence, the subject is hún, so vön is the correct form.

This is a very common Icelandic pattern meaning to be used to doing something or to be accustomed to doing something.

So:

• Hún er vön að borða kjúkling
  = She is used to eating chicken

With ekki, it becomes:

• Hún er ekki vön að borða kjúkling
  = She is not used to eating chicken

This is one of the standard ways to express be used to + -ing in English.

Because að is the infinitive marker here, like English to in to eat.

So:

• að borða = to eat
• að drekka = to drink
• að sofa = to sleep

After vera vanur/vön, Icelandic normally uses að + infinitive:

• Ég er vanur að vakna snemma.
  = I am used to waking up early.

So in your sentence:

• vön að borða = used to eating / used to eat

Because after að, Icelandic uses the infinitive, not a conjugated verb.

• borða = to eat / infinitive
• borðar = eats / present tense, usually with þú or hann/hún/það depending on context and form

Compare:

• Hún borðar kjúkling.
  = She eats chicken.

But:

• Hún er vön að borða kjúkling.
  = She is used to eating chicken.

So once you have að, the next verb stays in the infinitive form.

In a normal Icelandic main clause, the negation ekki usually comes after the finite verb.

Here the finite verb is er:

• Hún er ekki vön ...

That is the usual word order:

• subject + finite verb + ekki
  • rest

More examples:

• Ég kann ekki þetta.
  = I don't know this.
• Við förum ekki í dag.
  = We are not going today.

So er ekki is exactly what you would expect.

Because Icelandic does not have an indefinite article like English a/an.

So a bare noun often does the job:

• Ég borða fisk. = I eat fish.
• Hún borðar kjúkling. = She eats chicken.

In this sentence, kjúkling means chicken in a general food sense, not necessarily the chicken.

If Icelandic wants to say the chicken, it usually adds the definite article as a suffix:

• kjúklingurinn = the chicken (nominative singular)

But here the general, article-less form is the natural one.

Because kjúkling is in the accusative case, which is used here because borða takes a direct object.

The dictionary form is:

• kjúklingur = nominative singular

But as the object of borða, it becomes accusative:

• borða kjúkling = eat chicken

This is a very common pattern in Icelandic:

• hundur → hund
• hestur → hest
• kjúklingur → kjúkling

So kjúkling is the correct object form.

Á kvöldin is an idiomatic way to mean in the evenings or at night / in the evening regularly.

This expression is very common for repeated time periods:

• á morgnana = in the mornings
• á daginn = during the day / in the daytime
• á kvöldin = in the evenings

So:

• borða kjúkling á kvöldin
  = eat chicken in the evenings

Even though á often means on, in time expressions it can correspond to English in or during.

Because á kvöldin is a fixed, very common idiomatic expression for in the evenings.

The -in ending here is the definite article attached to the plural form, but in expressions like this Icelandic often uses the definite form where English would simply say in the evenings.

So this is something best learned as a chunk:

• á kvöldin = in the evenings
• á næturnar = at night / during the nights
• á sumrin = in the summers / during summertime

It may look a little unusual if you try to translate word-for-word, but it is natural Icelandic.

Here svo means so, therefore, or as a result.

It connects the two parts of the sentence:

• Hún er ekki vön að borða kjúkling á kvöldin, svo hún velur frekar núðlur.

That means:

• She isn't used to eating chicken in the evenings, so she chooses noodles instead / rather.

So svo is showing a consequence.

Depending on context, svo can also mean other things, like then, thus, or even be part of other expressions, but here so / therefore is the right idea.

Because the second part is a new clause, and Icelandic normally states the subject again.

So:

• ..., svo hún velur frekar núðlur.

This is very natural. English does the same thing:

• ..., so she chooses noodles.

You generally should not leave out hún here unless the structure is very different. Icelandic is not like some languages where the subject can easily be dropped just because it is understood.

Frekar means rather, preferably, or instead depending on context.

In this sentence:

• hún velur frekar núðlur

it means something like:

• she chooses noodles instead
• she would rather choose noodles
• she prefers noodles

It often expresses preference between alternatives.

Examples:

• Ég drekk frekar te en kaffi.
  = I’d rather drink tea than coffee.
• Hann fer frekar heim.
  = He prefers to go home / He goes home instead.

So here frekar shows that noodles are the preferred choice.

Because frekar is an adverb modifying the verb idea chooses ... rather/instead.

The natural Icelandic order is:

• velur frekar núðlur

This is similar to how English might say:

• chooses noodles instead
• would rather choose noodles

Adverbs in Icelandic often come before the noun they help introduce in expressions like this.

You may also see comparison structures such as:

• frekar en = rather than

For example:

• Hún velur frekar núðlur en hrísgrjón.
  = She chooses noodles rather than rice.

Because noodles are commonly treated as a plural item in Icelandic, just as they often are in English.

So:

• núðla = a noodle
• núðlur = noodles

In food contexts, the plural is usually the natural choice:

• Ég borða núðlur.
  = I eat noodles.

So velur frekar núðlur simply means chooses noodles instead.

Núðlur is the accusative plural here, because it is the direct object of velur (chooses).

The verb velja takes an object, and that object is typically in the accusative:

• velja eitthvað = choose something

So:

• hún velur núðlur

uses núðlur as the thing being chosen.

In this noun, the nominative plural and accusative plural happen to look the same, so you just see núðlur in both cases.

Yes. Velur is the present tense singular form of velja = to choose.

Examples:

• ég vel = I choose
• þú velur = you choose
• hún velur = she chooses

So:

• hún velur frekar núðlur
  = she chooses noodles instead

This is a useful verb to learn because it is common and slightly irregular.

Yes. Even if the meaning is already known, it is helpful to see how Icelandic maps onto natural English.

A close translation is:

• She is not used to eating chicken in the evenings, so she chooses noodles instead.

A slightly freer natural English version could be:

• She doesn’t usually eat chicken in the evening, so she prefers noodles.

But grammatically, the Icelandic structure is very clearly:

• Hún er ekki vön að ... = She is not used to ...
• svo = so
• hún velur frekar ... = she chooses ... instead / she rather chooses ...

So the sentence is straightforward Icelandic, even if the most natural English wording may shift a little.