Aunque le dije que descansara, mi madre siguió preparando la vinagreta.

Because descansara is the imperfect subjunctive, and it appears here after dije que because the meaning is not simple reported speech but a kind of request/instruction:

• Le dije que descansara = I told her to rest

In Spanish, when one person tries to influence another person’s action, the second verb often goes in the subjunctive.

A rough pattern is:

• decir que + indicative = to say that something is true
  
  • Dije que estaba cansada = I said that she was tired
• decir que + subjunctive = to tell/order/request that someone do something
  
  • Le dije que descansara = I told her to rest

So:

• descansó would mean she rested
• descansaba would mean she was resting / used to rest
• descansar would be the infinitive and does not fit after this structure

Yes. Descansara and descansase are both valid forms of the imperfect subjunctive.

So these mean the same thing:

• Le dije que descansara
• Le dije que descansase

In modern everyday Spanish, -ra forms are usually more common, especially in conversation.

Le is an indirect object pronoun, and here it means to her.

So:

• Le dije = I told her

The full idea is:

• Le dije a mi madre que descansara = I told my mother to rest

Spanish often uses a pronoun like le even when the person is later named explicitly.

Because with decir, the person you speak to is an indirect object, not a direct object.

The structure is:

• decir algo a alguien = to say something to someone

So:

• algo = the thing said
• a alguien = the person receiving it

That is why Spanish uses:

• le dije = I said to her / I told her

not:

• la dije

A native English speaker may expect her to act like a direct object, but Spanish treats it differently here.

Because Spanish often uses the pronoun and the noun together.

This is very common:

• Le dije a mi madre...
• Le di el libro a Juan
• Le expliqué la situación a Marta

The pronoun is not redundant in Spanish; it is a normal part of the structure. The noun phrase mi madre just makes clear who le refers to.

In your sentence, the subject of the second clause is also mi madre, so it helps keep everything clear:

• Aunque le dije que descansara, mi madre siguió preparando la vinagreta.

They are in the preterite because the sentence presents both actions as completed events in the past:

• dije = I told
• siguió = she continued

The speaker is narrating what happened:

1. I told her to rest.
2. She continued preparing the vinaigrette.

The preterite fits well for this kind of sequence in a story or report.

If you used the imperfect instead, the focus would be different, more like background or repeated action.

Because seguir + gerund means to keep doing or to continue doing something.

So:

• siguió preparando = she kept preparing / she continued preparing

If you said only:

• preparó la vinagreta

that would simply mean:

• she prepared the vinaigrette

But the original sentence emphasizes that she did not stop, even though she had been told to rest.

This structure is very common:

• siguió hablando = he kept talking
• seguimos esperando = we kept waiting
• siguieron trabajando = they continued working

Aunque means although / even though. It introduces a concession: something happened despite another fact.

Here:

• Aunque le dije que descansara... = Although I told her to rest...
• ...mi madre siguió preparando la vinagreta. = ...my mother kept preparing the vinaigrette.

So the idea is:

• I told her to rest,
• but despite that, she continued.

It is similar in meaning to aunque = even though in this sentence.

No. Aunque can be followed by either the indicative or the subjunctive, depending on the meaning.

A simple way to think about it:

• indicative: the speaker presents the information as a real fact
• subjunctive: the information is uncertain, hypothetical, or not presented as a confirmed fact

Examples:

• Aunque está cansada, trabaja.
  = Although she is tired, she works.
  Here her tiredness is treated as a fact.

• Aunque esté cansada, trabajará.
  = Even if she is tired, she will work.
  Here it is more hypothetical.

In your sentence, the subjunctive is not caused by aunque. It is caused by dije que descansara.

Because the sentence begins with a subordinate clause introduced by aunque, and Spanish normally separates that introductory clause from the main clause with a comma.

So:

• Aunque le dije que descansara, mi madre siguió preparando la vinagreta.

This is similar to English punctuation in sentences like:

• Although I told her to rest, my mother kept preparing the vinaigrette.

If the aunque clause came second, the comma might not be used in the same way:

• Mi madre siguió preparando la vinagreta aunque le dije que descansara.

Because Spanish uses the definite article more often than English.

Here la vinagreta refers to a specific vinaigrette being prepared in the situation. Spanish naturally uses the article in many cases where English might or might not.

Compare:

• Preparó la cena = She prepared dinner
• Lavó los platos = He washed the dishes
• Siguió preparando la vinagreta = She kept preparing the vinaigrette

English sometimes drops the article more freely; Spanish often keeps it.

Not really. A more natural interpretation is:

• I told her to rest

Word-for-word, it may look like:

• I said to her that she should rest

But in actual use, Spanish commonly expresses telling someone to do something with this kind of structure:

• Le dije que viniera = I told her to come
• Le dije que se sentara = I told her to sit down
• Le dije que descansara = I told her to rest

So you should learn it as a normal Spanish pattern, not as a strange literal translation.

Yes, absolutely. That is also correct.

This version makes the indirect object explicit inside the first clause:

• Aunque le dije a mi madre que descansara, siguió preparando la vinagreta.

The original sentence puts mi madre in the second clause as the subject:

• Aunque le dije que descansara, mi madre siguió preparando la vinagreta.

Both are natural. The original avoids repeating a mi madre inside the first clause and then uses mi madre clearly as the subject of siguió.