Hún finnur ekki varalitinn sinn og speglar sig þess vegna lengur í baðherberginu.

Because sinn is the reflexive possessive in Icelandic.

Icelandic uses sinn / sín / sitt when the thing belongs to the subject of the same clause. In this sentence, the subject is hún, and the lipstick belongs to her, so sinn is the natural choice.

• Hún finnur varalitinn sinn = she finds her own lipstick.
• Hún finnur varalitinn hennar would normally mean she finds someone else’s lipstick, belonging to another female person.

Also, sinn changes form to match the noun it goes with. Here varalitinn is masculine singular accusative, so the matching form is sinn.

Sig is the reflexive pronoun for the third person in the accusative.

The verb phrase spegla sig means to look at oneself in the mirror / to mirror oneself. Since the subject hún and the object are the same person, Icelandic uses sig:

• Hún speglar sig = she looks at herself in the mirror.

You cannot use hana here if you mean the subject herself. Hana would mean her as a different person.

It is based on the literal idea of mirroring, but in normal Icelandic spegla sig commonly means:

• to look at oneself in the mirror
• to check oneself in the mirror

So this is a standard reflexive expression, not just a poetic or unusual literal use.

Compare:

• spegla eitthvað = to mirror/reflect something
• spegla sig = to look at oneself in the mirror

Varalitinn is the noun varalitur in the definite singular accusative.

A useful breakdown is:

• varalitur = lipstick
• varalitinn = the lipstick

Icelandic usually adds the definite article to the end of the noun instead of using a separate word like the.

So here:

• dictionary form: varalitur
• form used in the sentence: varalitinn

Because it is the direct object of the verb finna.

The verb að finna normally takes an accusative object:

• finna eitthvað = to find something

So in this sentence:

• varalitinn is accusative because it is what she cannot find
• sinn also appears in accusative because it agrees with varalitinn

That agreement is important: the possessive sinn matches the noun in gender, number, and case.

Because í can take either dative or accusative, depending on whether you mean location or motion.

Here it means in the bathroom, as a location where she is already looking at herself, so Icelandic uses the dative:

• í baðherberginu = in the bathroom

If there were movement into the bathroom, you would use the accusative:

• Hún fer inn í baðherbergið = she goes into the bathroom

So the contrast is:

• location → dative
• motion toward/into → accusative

Þess vegna is a very common fixed phrase meaning:

• therefore
• because of that
• that’s why

It is often best learned as a set phrase.

Literally, it comes from the idea because of that:

• þess = of that
• vegna = because of / due to

But in normal use, you usually do not need to analyze it every time. Just recognize it as a common connector meaning therefore / so / that’s why.

This is because Icelandic main clauses usually follow the V2 pattern: the finite verb tends to come in the second position.

Here the first element is the subject:

• Hún = first position

So the finite verb comes next:

• finnur = second position

Then comes the negation:

• ekki

That gives:

• Hún finnur ekki ...

This placement is very normal in Icelandic main clauses.

No. Lengur is the comparative form, while lengi is the basic adverb.

• lengi = for a long time
• lengur = longer / for a longer time

So here lengur means she is looking at herself in the mirror for longer.

The comparison does not have to be stated explicitly. It can simply be understood from context, like longer than usual or longer than she otherwise would.

Also note that ekki lengur is a very common phrase meaning no longer, but that is not what is happening here. In this sentence, lengur is just an ordinary comparative adverb.

Because the second verb shares the same subject as the first one.

The sentence has two coordinated verb phrases:

• Hún finnur ekki varalitinn sinn
• og speglar sig þess vegna lengur í baðherberginu

The subject hún is understood for both verbs, so Icelandic does not need to repeat it.

You could repeat it:

• Hún finnur ekki varalitinn sinn og hún speglar sig þess vegna lengur í baðherberginu.

That is grammatical, but the version without the second hún is more compact and natural here.

Yes, but the word order may need to change.

The original clause is:

• og speglar sig þess vegna lengur í baðherberginu

That is natural because the subject is omitted and the second verb is simply coordinated with the first.

You can also front þess vegna, but then Icelandic V2 word order matters, and you normally need an explicit subject:

• ... og þess vegna speglar hún sig lengur í baðherberginu

Or as a new sentence:

• Hún finnur ekki varalitinn sinn. Þess vegna speglar hún sig lengur í baðherberginu.

So yes, þess vegna is movable, but moving it can affect the structure of the clause.

In Icelandic, reflexive possessives like sinn / sín / sitt refer back to the subject, but their form agrees with the possessed noun, not with the owner.

So:

• the reference goes back to hún
• the form matches varalitinn

Since varalitinn is:

• masculine
• singular
• accusative

the correct form is:

• sinn

This is a very important Icelandic pattern:

• who owns it? → decided by the subject
• what form does the possessive take? → decided by the noun being possessed