Sy is regtig slim, en my ouma vra haar dikwels om die kinders met huiswerk te help.

Because slim is a false friend for English speakers.

In Afrikaans, slim usually means clever, smart, or intelligent.

If you want to say thin/slender, you would usually use words like:

• maer = thin
• slank = slim/slender

So Sy is regtig slim means she is very intelligent, not that she is thin.

They are two different forms of the same pronoun:

• sy = she when it is the subject
• haar = her when it is the object

So:

• Sy is regtig slim = She is really clever
• my ouma vra haar = my grandmother asks her

English does the same thing:

• she is smart
• I ask her

Regtig means really.

It comes before slim because it is modifying the adjective, just like in English:

• really clever
• regtig slim

So the word order here is very similar to English.

Because slim is being used as a predicate adjective, after the verb is.

In Afrikaans, adjectives after linking verbs like is, was, and bly normally do not take an ending:

• Sy is slim
• Hy is moeg
• Hulle is gelukkig

So slim stays just slim here.

This is a very common Afrikaans pattern:

vra + person + om + infinitive

It means ask someone to do something.

So:

• my ouma vra haar = my grandmother asks her
• om ... te help = to help

Together:

• my ouma vra haar om die kinders met huiswerk te help
  = my grandmother asks her to help the children with homework

You can use the same pattern in other sentences too:

• Ek vra hom om te wag = I ask him to wait
• Sy vra my om te kom = She asks me to come

Afrikaans often uses a two-part infinitive frame:

• om ... te + verb

Here:

• om introduces the infinitive clause
• te marks the infinitive before the verb

So:

• om die kinders met huiswerk te help

English usually just uses to once, but Afrikaans often splits the structure into two parts.

Because in Afrikaans infinitive clauses, the main verb often goes to the end.

So in:

• om die kinders met huiswerk te help

the verb help comes last, and the other information comes before it:

• die kinders = the children
• met huiswerk = with homework
• te help = to help

This is very normal Afrikaans word order.

Compare:

Main clause:

• Sy help die kinders met huiswerk.

Infinitive clause:

• om die kinders met huiswerk te help

Because short object pronouns like haar, hom, my, jou often come before adverbs such as dikwels.

So:

• vra haar dikwels sounds very natural

This is a common Afrikaans pattern:

• Ek sien hom gereeld
• Sy help my altyd
• Ons nooi hulle dikwels

So the position of haar before dikwels is normal and idiomatic.

Yes. Dikwels means often.

It is a normal, standard word. Another common word is gereeld, which can mean regularly/often depending on context.

So:

• dikwels = often
• gereeld = regularly / often

In this sentence, dikwels tells you that this is a repeated or habitual action.

Because Afrikaans often uses the pattern:

help iemand met iets
= help someone with something

So here:

• die kinders = the people being helped
• met huiswerk = what they are being helped with

This works very much like English:

• help the children with homework

Because huiswerk is being used in a general sense, like homework in English.

So:

• met huiswerk = with homework in general

If you wanted to refer to specific homework, you could say:

• met die huiswerk = with the homework

But in general statements, huiswerk often appears without an article.

Yes. Afrikaans uses die as the definite article for both singular and plural nouns.

So:

• die kind = the child
• die kinders = the children

In this sentence:

• die kinders = the children

You tell whether it is singular or plural from the noun itself, not from the article.

Vra is in the present tense.

Afrikaans often uses the present tense for habits or repeated actions, just like English does:

• My ouma vra haar dikwels ... = My grandmother often asks her ...

The word dikwels is what makes the habitual meaning clear. Without it, vra would simply mean asks / is asking, depending on context.

Yes, many speakers do say vra vir haar, especially in everyday speech.

However, vra haar is also completely correct, and is often preferred in more careful or formal writing in this kind of structure.

So:

• vra haar om te help = correct
• vra vir haar om te help = also common, especially colloquially

For a learner, the important thing is that the version in your sentence is perfectly natural and correct.