Hon ville inte gå ut, och hennes syster orkade heller inte följa med.

They are both in the past tense (the Swedish preterite).

• ville = past tense of vilja (to want)
• orkade = past tense of orka (to have the energy/strength to)

So the sentence is talking about a situation in the past.

Because this is normal Swedish main clause word order.

In a main clause, when the subject comes first, the finite verb usually comes next, and inte comes after that:

• Hon ville inte gå ut
• Hennes syster orkade heller inte följa med

This is part of Swedish V2 word order. A useful comparison:

• Main clause: Hon ville inte gå ut
• Subordinate clause: ... att hon inte ville gå ut

So the position of inte is very typical here.

Because after verbs like vilja and orka, Swedish normally uses the bare infinitive.

So you say:

• vilja gå
• orka följa

not:

• vilja att gå
• orka att följa

This is similar to English in phrases like want to go, except Swedish often does not need an extra word corresponding to to after certain verbs.

Orka is a very common Swedish verb, and it does not just mean can.

It usually means something like:

• have the energy to
• have the strength to
• be up to
• manage to, because you still have enough energy or motivation

So hennes syster orkade heller inte följa med suggests that the sister didn’t have the energy, strength, or motivation to come along either.

That is different from kunna, which is more about ability in general.

Here heller means either in a negative sentence.

So:

• orkade heller inte följa med = didn’t have the energy to come along either

A very useful rule is:

• också = also / too in positive statements
• heller = either in negative statements

For example:

• Hon ville också gå ut = She also wanted to go out.
• Hon ville inte heller gå ut = She didn’t want to go out either.

Yes. Hennes syster orkade inte heller följa med is also natural Swedish.

Both heller inte and inte heller are used, and the difference is often mainly one of rhythm or emphasis, not basic meaning.

So these are both fine:

• Hennes syster orkade heller inte följa med
• Hennes syster orkade inte heller följa med

For a learner, the important thing is that both mean didn’t ... either.

Because sin/sitt/sina can only refer back to the subject of the same clause.

In the second clause, the subject is:

• hennes syster

If you want to show that the sister belongs to the woman mentioned earlier (hon), Swedish uses hennes.

So:

• hennes syster = her sister

You cannot use sin to refer back across into the previous clause. That is why hennes is correct here.

A useful comparison:

• Hon tog på sig sin jacka = She put on her own jacket.
  Here sin refers back to hon in the same clause.

Yes. They are very common Swedish verb + particle combinations, and it helps to learn them as whole units.

• gå ut = go out / go outside
• följa med = come along / join / accompany

The individual words are:

• gå = go
• ut = out
• följa = follow
• med = with

But the full combinations often have meanings that are more natural than translating each word separately. For example, följa med is often best understood as come along rather than literally follow with.

It can mean either, depending on context.

Possible meanings include:

• go outside
• go out in general
• go out socially or for the evening

So Hon ville inte gå ut could mean:

• she didn’t want to leave the house
• she didn’t want to go out somewhere
• she didn’t want to go out socially

You usually need context to know which one is meant.

Because Swedish often links two related statements with och, even when English might think in terms of and ... either or neither.

So this pattern is very normal:

• statement 1
• och
  • statement 2 with heller inte

That gives:

• Hon ville inte gå ut, och hennes syster orkade heller inte följa med.

Swedish does have other ways to express a similar idea, for example:

• Inte heller hennes syster orkade följa med.
• Varken hon eller hennes syster orkade följa med.

But the original sentence is completely natural and idiomatic.

Because följa med is the standard Swedish expression for come along, join someone, or accompany someone.

So if one person is going somewhere and another person joins them, Swedish very often uses följa med:

• Vill du följa med? = Do you want to come along?
• Hon följde med oss. = She came with us.

This is one of those expressions that is best memorized as a chunk, because the natural English translation is usually not a word-for-word one.