Ef hún væri ekki svona kvíðin, myndi hún ekki hika svona lengi.

Væri is the subjunctive form of vera (to be). It is used here because the sentence expresses a hypothetical / unreal situation:

• Ef hún væri ekki svona kvíðin ... = If she were not so anxious ...

This is not describing a simple fact. It is talking about an imagined situation contrary to reality or at least not presented as real.

Compare:

• Ef hún er ekki svona kvíðin ... = If she is not so anxious ...
  This sounds like a real possibility.
• Ef hún væri ekki svona kvíðin ... = If she were not so anxious ...
  This sounds hypothetical or counterfactual.

So væri is used because the sentence means something like if she weren’t so anxious.

Myndi is the conditional form of munu, and here it works like would in English.

So:

• myndi hún ekki hika = she would not hesitate

This matches the hypothetical sense created by væri in the first clause. Icelandic often uses this pattern for unreal conditionals:

• Ef ... væri ..., myndi ...
• If ... were ..., would ...

So the structure is very close to English:

• If she weren’t so anxious, she wouldn’t hesitate so long.

Yes, that is the most natural way to understand it.

The pattern:

• Ef
  • subjunctive (væri)
• conditional main clause with myndi

usually signals an unreal or imagined condition.

So the sentence suggests:

• she is anxious
• and because of that, she does hesitate for a long time

The speaker is imagining the opposite situation:

• If she were not so anxious, she would not hesitate so long.

That is why English learners often feel the sentence corresponds to If she weren’t..., she wouldn’t...

Because each clause is negated separately.

1. Ef hún væri ekki svona kvíðin
   = If she were not so anxious

2. myndi hún ekki hika svona lengi
   = she would not hesitate so long

Each ekki belongs to its own clause.

This is exactly like English:

• If she were not so anxious, she would not hesitate so long.

You need both negatives because the sentence says two separate negative things:

• she is imagined as not anxious
• and in that imagined situation, she would not hesitate

This is because of Icelandic verb-second word order in main clauses.

After the if-clause comes the main clause:

• Ef hún væri ekki svona kvíðin, myndi hún ekki hika svona lengi.

In Icelandic main clauses, the finite verb usually comes in the second position. Since the first position is effectively occupied by the preceding clause, the finite verb comes next:

• [Ef hún væri ekki svona kvíðin], [myndi] [hún] ...

This is very common in Icelandic.

Compare:

• Hún myndi ekki hika svona lengi.
  = neutral word order when the sentence starts with hún
• Ef hún væri ekki svona kvíðin, myndi hún ekki hika svona lengi.
  = after the initial subordinate clause, the finite verb comes first in the main clause

So myndi hún is the expected word order here.

Svona often means so, like this, or this way, depending on context.

In this sentence it appears twice, but each one modifies something different:

1. svona kvíðin
   = so anxious / this anxious

2. svona lengi
   = so long / for this long

So the sentence has the pattern:

• not so anxious
• not hesitate so long

English also allows this kind of repetition:

• If she weren’t so anxious, she wouldn’t hesitate so long.

So there is nothing strange grammatically about having svona twice.

Kvíðin is an adjective meaning anxious / nervous, and here it is a predicate adjective after vera (to be).

It agrees with hún:

• hún = feminine singular
• so the adjective is also feminine singular nominative

That is why you get kvíðin here.

In other contexts, the adjective would change form depending on gender, number, case, and whether it is weak or strong.

Here the important point is simply:

• hún væri kvíðin = she were anxious

So the form matches the subject.

Hika is the infinitive of the verb to hesitate.

After myndi, Icelandic uses the infinitive:

• myndi hika = would hesitate

This is similar to English:

• would hesitate

The finite verb is myndi, and hika stays in the infinitive.

So in:

• myndi hún ekki hika

  the grammatical tense/mood information is carried by myndi, not by hika.

Because lengi is an adverb, and here it modifies the verb phrase hika.

• hika lengi = hesitate for a long time
• svona lengi = this long / so long

An adjective such as langur would be used to describe a noun:

• langur dagur = a long day

But in this sentence, there is no noun being described. The sentence is describing how long she hesitates, so an adverb is needed:

• lengi

Yes, but it would change the meaning.

• Ef hún er ekki svona kvíðin, ...
  = If she is not this anxious, ...
  This sounds more like a real condition or open possibility.

• Ef hún væri ekki svona kvíðin, ...
  = If she were not this anxious, ...
  This sounds hypothetical or contrary to fact.

So the original sentence is specifically choosing the more unreal, imagined meaning.

A useful rule is that ekki often comes after the finite verb, or after the subject if the finite verb has moved to first/second position.

In this sentence:

• hún væri ekki ...
• myndi hún ekki hika ...

In the second clause, the finite verb myndi comes first because of word order rules, then the subject hún, and then ekki.

So:

• myndi hún ekki hika

is the normal order here.

For English speakers, it can help to think of ekki as often sitting relatively early in the clause, but not necessarily in exactly the same position as not in English.

Usually it is very close, but not always identical in nuance.

Kvíðinn / kvíðin / kvíðið often means:

• anxious
• nervous
• sometimes worried depending on context

In this sentence, the idea is that she is emotionally tense enough that it affects her behavior and makes her hesitate. So anxious or nervous would both fit well, depending on the translation you were shown.

Yes, the comma is standard here because the sentence begins with a subordinate if-clause:

• Ef hún væri ekki svona kvíðin, myndi hún ekki hika svona lengi.

The comma helps separate:

• the conditional clause
• the main clause

This is normal Icelandic punctuation and also makes the structure easier to read.