Mi hermana quiere hacerse unas mechas, pero primero necesita hablar con la peluquera.

Here hacerse means to get something done to oneself.

So hacerse unas mechas is not literally to make oneself some highlights. It means to have highlights done, or more naturally in English, to get highlights.

The reflexive se is very common in Spanish for personal grooming or beauty treatments:

• hacerse las uñas = to get one’s nails done
• hacerse un tatuaje = to get a tattoo
• hacerse un corte de pelo = to get a haircut

It often suggests that the person is arranging the treatment for themselves, even if someone else actually performs it.

Because after querer (to want), Spanish normally uses an infinitive:

• quiere + infinitive = wants to ...

So:

• Mi hermana quiere hacerse unas mechas = My sister wants to get highlights

The verb hacerse stays in the infinitive because it depends on quiere.

This same pattern appears all the time:

• Quiero comer = I want to eat
• Quiere salir = He/She wants to go out
• Queremos comprarlo = We want to buy it

With a conjugated verb plus an infinitive, Spanish often lets pronouns go in either place:

• Mi hermana se quiere hacer unas mechas
• Mi hermana quiere hacerse unas mechas

Both are grammatically correct.

In this sentence, quiere hacerse sounds very natural. Attaching the pronoun to the infinitive is especially common in everyday Spanish.

In Spain, mechas usually means highlights or streaks in the hair.

So hacerse unas mechas means to get highlights.

Depending on context, mechas can refer to different highlighting techniques or lighter strands in the hair. In everyday use, it is a very common word at the hair salon.

Spanish often uses an article where English might not.

So:

• hacerse unas mechas = to get some highlights / to get highlights

The unas does not necessarily mean a specific number. It often just makes the phrase sound natural and idiomatic.

Compare:

• hacerse unas mechas = natural
• hacerse mechas = possible, but less idiomatic in this context

This is similar to other salon expressions:

• hacerse un corte de pelo = to get a haircut
• ponerse unas extensiones = to get some extensions

Because necesitar can be followed directly by an infinitive.

• necesitar + infinitive = to need to do something

So:

• necesita hablar = she needs to speak

Examples:

• Necesito estudiar = I need to study
• Necesitan salir = They need to leave

You may also see necesitar algo:

• Necesito ayuda = I need help

But when a second verb follows, Spanish usually uses the infinitive directly.

Because hablar con means to speak with / to talk to someone.

In Spanish, hablar con alguien is the normal choice when you mean having a conversation with someone.

• hablar con la peluquera = to speak with the hairdresser

You can sometimes hear hablar a alguien, but it often sounds more like to speak at someone or is less neutral in many contexts. For a normal conversation, hablar con is the safest and most natural choice.

Peluquera is the feminine form of peluquero/peluquera, meaning hairdresser.

Because the sentence refers to a female hairdresser, it uses:

• la peluquera

If it were a male hairdresser, it would be:

• el peluquero

Also note the difference between:

• peluquera = hairdresser
• peluquería = hair salon / hairdresser’s shop

Primero means first.

In this sentence:

• pero primero necesita hablar con la peluquera
• but first she needs to talk to the hairdresser

It signals the order of actions:

1. talk to the hairdresser
2. then get the highlights

Its position is flexible, but the sentence given is very natural. You could also hear:

• pero necesita hablar primero con la peluquera

Both are correct, with only a slight shift in emphasis.

In Spanish, possessive words like mi, tu, su, nuestro usually replace the article.

So you say:

• mi hermana = my sister
  not la mi hermana

This is different from some older forms of Spanish or some other languages, but in modern standard Spanish, mi hermana is the normal form.

Yes, especially because of mechas, which is a very normal salon word in Spain.

The whole sentence sounds natural in Spain:

• Mi hermana quiere hacerse unas mechas, pero primero necesita hablar con la peluquera.

In other Spanish-speaking regions, the vocabulary around hair treatments can vary a bit, but this sentence is perfectly standard and easy to understand.