Hún varð svo hissa að hún sagði ekki neitt í smástund.

Varð is the past tense of verða, which often means to become.

So Hún varð svo hissa literally means She became so surprised.
In natural English, that often comes out as She was so surprised or She got so surprised/shocked depending on context.

This is a very common Icelandic pattern:

• verða + adjective = become/get + adjective

For example:

• hann varð reiður = he got angry
• ég varð þreytt(ur) = I got tired

Hissa is one of those Icelandic adjectives that usually does not change form the way many other adjectives do.

So you can say:

• hún er hissa
• hann er hissa
• þau eru hissa

That may feel unusual if you are expecting adjective agreement endings everywhere, but hissa is commonly used as an indeclinable adjective in modern Icelandic.

Svo ... að means so ... that.

In this sentence:

• svo hissa að ... = so surprised that ...

So the structure is:

• Hún varð svo hissa að ...
• She became so surprised that ...

This is a very useful construction in Icelandic:

• Hann var svo þreyttur að hann sofnaði strax.
  He was so tired that he fell asleep immediately.

• Það var svo kalt að ég fór heim.
  It was so cold that I went home.

Because að introduces a new clause, and that clause needs its own subject.

So the sentence has two parts:

1. Hún varð svo hissa
2. að hún sagði ekki neitt í smástund

Literally:

1. She became so surprised
2. that she said nothing for a moment

In English, we also repeat the subject in this kind of sentence:
She was so surprised that she didn’t say anything for a moment.

Yes, Icelandic commonly uses what looks like a double negative in English terms, but it is normal grammar in Icelandic.

• ekki = not
• neitt = anything / nothing, depending on the negative context

So:

• sagði ekki neitt literally looks like said not anything
• natural English: didn’t say anything or said nothing

This is standard Icelandic usage, not an error.

Similar examples:

• Ég sá ekki neinn. = I didn’t see anyone.
• Hann gerði ekki neitt. = He didn’t do anything.

Neitt is the neuter singular accusative form of enginn / ekkert / engin(n)-type negative/indefinite usage in this construction.

Here it works as the object of sagði in the sense of say anything.

You do not need to think of it as a direct word-for-word match to English. The important pattern is:

• ekki neitt = not anything / nothing

This is a very common chunk to memorize.

Í smástund means for a short while, for a moment, or briefly.

• stund = a while / a period / a moment
• smá = small / little

Together, smástund is basically a short moment.

With í, the phrase means something like:

• for a little while
• for a brief moment

So:

• hún sagði ekki neitt í smástund = she didn’t say anything for a moment

Icelandic often uses í with expressions of duration in fixed phrases like this.

So í smástund is an idiomatic way to say:

• for a moment
• for a short while

You should learn it as a set phrase.

Other time expressions may use different prepositions or no preposition at all, so it is not always best to translate prepositions directly from English.

This is because Icelandic is generally a verb-second language in main clauses, but subordinate clauses behave differently.

Main clause:

• Hún varð svo hissa ...

The finite verb varð comes very early, which fits normal Icelandic main-clause word order.

Subordinate clause after að:

• að hún sagði ekki neitt ...

Here the subject hún comes before the verb sagði, which is normal in this kind of subordinate clause.

So this sentence shows a very common contrast:

• main clause: verb-second behavior
• subordinate clause: more straightforward subject + verb order

In this sentence, svo is part of the full pattern svo ... að, so it means so ... that.

By itself, svo can have several meanings depending on context, including:

• so
• thus
• then
• sometimes an intensifying sense depending on structure

But here, the meaning is clearly tied to the result clause:

• svo hissa að ... = so surprised that ...

Not necessarily. Hissa usually means surprised, astonished, or taken aback, depending on context and tone.

The strength comes partly from the surrounding words:

• svo hissa = so surprised

So the sentence gives a fairly strong reaction, but hissa itself does not always have to be extremely dramatic.

Yes, depending on context, that can be a reasonable translation.

A more literal translation is:

• She became so surprised that she said nothing for a moment.

But natural English might also use:

• She was so surprised that she didn’t say anything for a moment.
• She was so stunned that she didn’t say anything for a moment.
• She was so shocked that she didn’t say anything for a moment.

The best English version depends on the tone of the broader context.

Because Icelandic often uses segja (say) in places where English might choose either say or speak depending on style.

Here, sagði ekki neitt literally means said nothing, which is a very natural way in Icelandic to express that she was silent.

English can also say:

• she said nothing
• she didn’t say anything

If you used a verb closer to speak, the nuance might shift slightly toward the act of talking in general rather than the absence of any utterance at all.

Both instances of hún are in the nominative, because each one is the subject of its clause.

• Hún varð ... → hún is the subject of varð
• að hún sagði ... → hún is the subject of sagði

So even though the sentence has two clauses, each hún is doing the same grammatical job in its own clause.