Nie net die buurvrou nie, maar ook haar dogter groet my oor die heining.

This is a very common question. Here, nie ... nie is not making the sentence negative in the usual sense.

The pattern nie net ... nie, maar ook ... means not only ... but also ...

So:

• nie net = not only
• the second nie closes that first part
• maar ook = but also

So the structure is:

Nie net X nie, maar ook Y ...
= Not only X, but also Y ...

In other words, the two nie words belong to a fixed expression here.

Maar ook means but also.

It introduces the second part of the pair:

• Nie net die buurvrou nie = not only the neighbour
• maar ook haar dogter = but also her daughter

So maar ook adds another person to the subject.

Because the whole phrase

Nie net die buurvrou nie, maar ook haar dogter

is the subject of the sentence.

In Afrikaans main clauses, the finite verb usually comes in the second position, but that does not mean it has to be the second word. It comes after the first whole unit of the sentence.

Here the first whole unit is the complete subject:

Nie net die buurvrou nie, maar ook haar dogter | groet my oor die heining.

So groet comes after the entire subject phrase, not after the first noun.

Afrikaans verbs do not change the way English verbs do.

In English, you might compare:

• she greets
• they greet

But in Afrikaans, the verb usually stays the same:

• sy groet
• hulle groet

So even though the subject includes both die buurvrou and haar dogter, the verb is still simply groet.

Yes. Here my means me.

That can be confusing for English speakers, because Afrikaans my can look like English my, but in this sentence it is the object pronoun:

• groet my = greets me / says hello to me

You can tell from its position after the verb and from the meaning of the sentence.

Buurvrou means female neighbour or the woman next door.

It is a compound noun:

• buur = neighbour
• vrou = woman

Afrikaans often forms compounds as one word, so buurvrou is written together.

If you wanted a more general word for neighbour, regardless of gender, you would often use buurman for a male neighbour and buurvrou for a female neighbour, depending on the person being referred to.

Because die and haar do different jobs.

• die buurvrou = the neighbour
  Here die is the definite article: the.

• haar dogter = her daughter
  Here haar is a possessive determiner: her.

In Afrikaans, just as in English, you normally do not combine the and her before the same noun.

So:

• die buurvrou = the neighbour
• haar dogter = her daughter

not die haar dogter.

Oor die heining literally means over the fence.

In this sentence it means that the greeting happens across or over the fence between properties. It is a very natural kind of neighbourly image.

So the idea is something like:

• the neighbour and her daughter greet me over/across the fence

It does not suggest that they are climbing the fence; it just describes where the greeting happens.

Yes, in normal writing this comma is standard.

The sentence has the paired structure:

Nie net ... nie, maar ook ...

The comma helps separate the two balanced parts:

• Nie net die buurvrou nie
• maar ook haar dogter

So the comma is not random; it marks the contrast-and-addition structure clearly.

Yes. That is another correct and common way to express the same idea.

For example:

Nie alleen die buurvrou nie, maar ook haar dogter groet my oor die heining.

This also means Not only the neighbour, but also her daughter greets me over the fence.

A few common variants are:

• nie net ... nie, maar ook ...
• nie alleen ... nie, maar ook ...
• nie slegs ... nie, maar ook ...

Nie net ... nie, maar ook ... is very natural and common in everyday Afrikaans.