Min søster er uenig, for hun vil hellere have ost end honning på sin bolle.

Uenig is an adjective meaning in disagreement or not in agreement.

So Min søster er uenig is literally My sister is in disagreement / is not in agreement, which is the natural Danish way to say My sister disagrees in many contexts.

A few useful points:

• enig = in agreement
• uenig = not in agreement, disagreeing
• at være uenig = to disagree

So Danish often uses to be + adjective where English might prefer a verb:

• Jeg er enig = I agree
• Jeg er uenig = I disagree

Both for and fordi can mean because, but they are used a bit differently.

In this sentence, for introduces an explanation:

• Min søster er uenig, for hun vil hellere have ost ...

This sounds like:

• My sister disagrees, because she would rather have cheese...

The important grammar difference is word order:

• After for, Danish keeps normal main-clause word order:
  • for hun vil ...
• After fordi, Danish often uses subordinate-clause word order:
  • fordi hun hellere vil have ...

So these are both possible, but not identical in structure:

• ... for hun vil hellere have ost ...
• ... fordi hun hellere vil have ost ...

For learners, a simple rule is:

• for = coordinating conjunction, more like giving an explanation afterward
• fordi = subordinating conjunction, more directly means because

This is because for is a coordinating conjunction, so the clause after it stays a main clause.

Main-clause word order in Danish usually places the finite verb early:

• hun vil hellere have ...

So the pattern is:

• subject: hun
• finite verb: vil
• adverb: hellere
• infinitive: have

If you used fordi instead, you would often get:

• fordi hun hellere vil have ...

That difference is very common in Danish and often confusing for English speakers.

Hellere means rather or preferably.

In this sentence, vil hellere have means:

• would rather have
• prefers to have

So:

• hun vil hellere have ost end honning = she would rather have cheese than honey

A useful comparison:

• gerne = gladly, willingly
• hellere = rather
• helst = preferably, most of all

Examples:

• Jeg vil gerne have kaffe. = I would like coffee.
• Jeg vil hellere have te. = I would rather have tea.
• Jeg vil helst have te. = I would prefer tea most of all.

In Danish, vil have is very common when talking about what someone wants to eat, drink, receive, or choose.

So hun vil hellere have ost literally means she wants rather to have cheese, but in natural English that becomes she would rather have cheese.

This is a very normal Danish structure:

• Jeg vil have vand. = I want water.
• Han vil hellere have kage. = He would rather have cake.

So even though English might think in terms of prefer, Danish often uses vil hellere have.

Because Danish uses end after a comparative word such as hellere.

So:

• hellere ... end ... = rather ... than ...

Examples:

• Jeg vil hellere gå end løbe. = I would rather walk than run.
• Hun spiser hellere ost end honning. = She would rather eat cheese than honey.

English speakers sometimes expect something like than, and in Danish that word is end.

This is a very important Danish grammar point.

Sin/sit/sine is a reflexive possessive. It is used when the owner is the subject of the clause.

Here, the subject of the clause is hun, and the bun belongs to hun, so Danish uses sin:

• hun ... på sin bolle = on her own bun

If you said hendes bolle, it would normally mean someone else’s bun, belonging to another female person, not the subject.

Compare:

• Hun smører ost på sin bolle. = She spreads cheese on her own bun.
• Hun smører ost på hendes bolle. = She spreads cheese on her bun, but her refers to some other woman/girl.

Because the form of the reflexive possessive depends on the noun that follows:

• sin for common gender singular nouns
• sit for neuter singular nouns
• sine for plural nouns

Here the noun is bolle, which is a common gender singular noun, so the correct form is sin.

Examples:

• sin bog = her/his own book
• sit hus = her/his own house
• sine sko = her/his own shoes

Here, bolle means a bread roll or bun.

In the sentence, it refers to a small piece of bread that you put toppings on, such as cheese or honey.

This is a common everyday Danish word, but learners should know that bolle can have other meanings in other contexts, including slang meanings. In a food sentence like this one, though, it clearly means bread roll/bun.

Yes. På is the normal preposition for something placed on bread.

So Danish says:

• ost på brød
• smør på bollen
• honning på sin bolle

This works very much like English on in this context.

Yes, but it would not be exactly the same structure.

With hellere, the normal pattern is:

• hellere ... end ...

So in this sentence, ost end honning is the expected choice.

You can use frem for in other sentences to mean instead of or rather than, for example:

• Hun vælger ost frem for honning. = She chooses cheese rather than honey.

So:

• hellere ... end ... is the most natural pattern here
• frem for is possible in differently built sentences

Yes, it is natural and grammatical.

It sounds like normal everyday Danish:

• Min søster er uenig sets up the disagreement
• for gives the reason
• hun vil hellere have ost end honning explains the preference
• på sin bolle gives the context

A very similar alternative with fordi would also be natural:

• Min søster er uenig, fordi hun hellere vil have ost end honning på sin bolle.

Both are good Danish; they just differ a little in style and word order.