I prøverommet så hun at størrelsen var feil, men hun lot være å klage fordi køen var lang.

Because Norwegian is a V2 language in main clauses. That means the finite verb normally has to come in the second position.

So when I prøverommet is placed first for emphasis or setting, the verb så must come next:

• Hun så at størrelsen var feil. = She saw that the size was wrong.
• I prøverommet så hun at størrelsen var feil. = In the fitting room, she saw that the size was wrong.

So the order becomes:

• I prøverommet = first element
• så = finite verb in second position
• hun = subject after the verb

This is very common in Norwegian.

Prøverommet means the fitting room or the changing room, especially in a shop.

It comes from:

• å prøve = to try
• rom = room
• prøverom = fitting room / changing room
• prøverommet = the fitting room

The ending -et is the definite ending for a neuter noun here.

Norwegian usually uses i for being inside an enclosed space.

So:

• i prøverommet = in the fitting room

Using på would sound wrong here, because a fitting room is understood as a room or enclosed area, not a surface or a more abstract location.

This is similar to:

• i butikken = in the shop
• i bilen = in the car
• i huset = in the house

Here så is the past tense of å se = to see.

• å se = to see
• ser = sees / see
• så = saw
• har sett = has seen

So in this sentence:

• så hun at ... = she saw that ...

This is not the conjunction så meaning so.

Størrelsen means the size.

In context, the speaker is talking about the size of a specific item, so Norwegian naturally uses the definite form:

• en størrelse = a size
• størrelsen = the size

In a fitting-room situation, it is already clear which size is meant: the size of the clothing item she is trying on.

So størrelsen var feil means the size was wrong.

Yes. In this sentence, feil means wrong / incorrect.

So:

• størrelsen var feil = the size was wrong

Norwegian often uses feil in this way:

• Det er feil. = That is wrong.
• Jeg tok feil buss. = I took the wrong bus.
• Nummeret er feil. = The number is wrong.

You could also hear something like feil størrelse = wrong size, but størrelsen var feil is a natural full clause meaning that the size turned out to be wrong.

Lot være å is part of the expression å la være å, which means:

• to refrain from
• to avoid
• to not do something on purpose

So:

• hun lot være å klage = she refrained from complaining / she chose not to complain

This is an idiomatic expression, and it is very common in Norwegian.

Forms of the verb:

• å la være å = to refrain from
• lar være å = refrains from
• lot være å = refrained from
• har latt være å = has refrained from

Because å klage is an infinitive, and the expression å la være å + infinitive requires it.

Structure:

• å la være å + infinitive

Examples:

• Hun lot være å klage. = She refrained from complaining.
• Jeg lar være å svare. = I refrain from answering.
• De lot være å gå. = They chose not to go.

So the second å belongs with the infinitive verb klage.

No, in a sentence like this Norwegian normally needs the subject again in the new clause.

So:

• ..., men hun lot være å klage ...

is correct.

You would not normally say:

• ..., men lot være å klage ...

because the second clause needs its own subject.

This is similar to English:

• ..., but she refrained from complaining ...

Because fordi introduces a subordinate clause, and subordinate clauses do not follow the main-clause V2 pattern.

So:

• Main clause: I prøverommet så hun ...
• Subordinate clause: fordi køen var lang

In the fordi clause, the normal order is:

• subject + verb
• køen var lang = the queue was long

You do not invert the subject and verb there.

Compare:

• Hun dro ikke. = She didn’t leave.
• ... fordi hun var trøtt. = ... because she was tired.

Køen means the queue or the line.

It comes from:

• ei/en kø = a queue / line
• køen = the queue / line

It is definite because it refers to the specific queue that was there in the situation, for example the line at the shop counter.

So:

• fordi køen var lang = because the queue was long

Yes, very much so.

Here it connects two contrasting ideas:

• She saw the size was wrong,
• but she did not complain.

So:

• men = but

The sentence structure is very similar to English in that respect.

Because men joins two full clauses here, and Norwegian normally uses a comma before men in this kind of sentence.

So the sentence is divided like this:

• I prøverommet så hun at størrelsen var feil,
• men hun lot være å klage fordi køen var lang.

The comma helps show the contrast and the clause boundary.

Sometimes in informal speech or writing, at may be omitted in some contexts, but here at is completely natural and standard.

• så hun at størrelsen var feil = she saw that the size was wrong

For learners, it is safest to keep at in sentences like this.

Yes. Å klage is the standard verb for to complain.

Examples:

• Hun klaget. = She complained.
• Han klager mye. = He complains a lot.
• De ville klage. = They wanted to complain.

So hun lot være å klage is a very natural way to say she refrained from complaining or she chose not to complain.