Learn Hardcore Spanish (Spain): Mi hermana se peina antes de salir de casa. - My sister combs her hair before leaving the house.

peinar (without reflexive pronoun) = to comb someone else’s hair.
- Yo peino a mi hijo. = I comb my son’s hair.
peinarse (with me/te/se/nos/os/se) = to comb your own hair.
- Yo me peino. = I comb my hair.
- Ella se peina. = She combs her hair.

So peinar focuses on the object (another person), and peinarse focuses on the subject’s own hair.

Why doesn’t the sentence say el pelo? Shouldn’t it be Mi hermana se peina el pelo?

You can say:

Mi hermana se peina el pelo antes de salir de casa.

But in everyday speech, Spanish often drops the noun when it is obvious from context, especially with routine grooming actions:

se lava (understood: herself, her body)
se afeita (understood: his face / her legs, etc.)
se peina (understood: her hair)

So Mi hermana se peina is normally understood as “My sister does her hair / combs her hair.” Adding el pelo is more explicit but not necessary.

Could I say Mi hermana peina su pelo instead of Mi hermana se peina?

You could say it grammatically, but it is:

Unusual sounding, and
Ambiguous.

Mi hermana peina su pelo could be interpreted as:

My sister combs her own hair, or
My sister combs someone else’s hair (because su can mean his, her, their, your).

The natural, idiomatic way to say “my sister combs her hair” is:

Mi hermana se peina (el pelo).

Use peinar without se mainly when the person whose hair is being combed is not the subject:

Mi hermana peina a su hija. = My sister combs her daughter’s hair.

Why is there no subject pronoun ella? Why not Ella se peina…?

Spanish usually omits subject pronouns when the subject is already clear from:

the verb ending, and/or
a noun subject.

Here the subject mi hermana is explicit, so ella would be redundant:

Mi hermana se peina… ✅ (normal)
Ella se peina… ✅ (also correct, just a different subject: She combs her hair…)
Mi hermana ella se peina… ❌ (ungrammatical / very odd)

You would typically use ella only if you need to contrast or stress it:

Mi hermano es calvo, pero ella se peina todos los días.
(My brother is bald, but she does her hair every day.)

Why is it antes de salir and not just antes salir?

In Spanish, when antes de is followed directly by a verb, that verb must be in the infinitive, and you must keep de:

antes de + infinitive
- antes de comer = before eating
- antes de salir = before going out / before leaving

So:

Mi hermana se peina antes de salir. ✅
Mi hermana se peina antes salir. ❌ (you cannot drop de here)

What’s the difference between antes de salir and antes de que salga?

Both can relate to “before leaving,” but:

antes de + infinitive
- Used when the subject is the same in both actions:
  - Mi hermana se peina antes de salir.
    (My sister combs her hair before leaving. She combs, and she leaves.)
antes de que + subjunctive
- Used when the subject is different, or when you want a full clause:
  - Me peino antes de que mi hermana salga.
    (I do my hair before my sister leaves.)
  - Me peino antes de que salgas.
    (I do my hair before you leave.)

So in the original sentence, antes de salir is correct because mi hermana both combs her hair and leaves the house.

Why is it salir de casa and not salir la casa?

In Spanish, salir (to go out / to leave) normally takes the preposition de when you say where you are leaving from:

salir de un lugar = to go out of / leave a place
- salir de casa = leave (the) house
- salir de la oficina = leave the office
- salir de Madrid = leave Madrid

So:

salir de casa ✅
salir la casa ❌ (you must use de)

Why is it de casa and not de la casa?

Both exist, but there is a nuance:

de casa (no article) → usually means “from home” in a general, personal sense.
- Salgo de casa a las ocho. = I leave home at eight.
de la casa (with article) → more literal/physical, referring to a specific house as a building.
- Salimos de la casa en ruinas. = We went out of the ruined house.

In daily routine sentences like this one, de casa without la is the natural choice, because it means “from home”:

Mi hermana se peina antes de salir de casa.
= My sister does her hair before leaving home.

Does salir de casa mean “to go out” in the sense of partying, or just physically leaving the house?

Salir de casa by itself refers to physically leaving home. It doesn’t necessarily mean going out socially.

Mi hermana se peina antes de salir de casa.
= She does her hair before leaving home (maybe to work, school, etc.)

For “going out” socially, you would usually specify:

salir de fiesta = to go out partying
salir a cenar = to go out for dinner
salir con amigos = to go out with friends

How would the sentence change if the subject were I or we?

You change the possessive and the reflexive pronoun + verb ending:

Yo (I):
- Yo me peino antes de salir de casa.
  = I do my hair before leaving home.
Nosotros / Nosotras (we):
- Nosotros nos peinamos antes de salir de casa. (group including at least one man)
- Nosotras nos peinamos antes de salir de casa. (all women)
  = We do our hair before leaving home.

Pattern for peinarse in the present:

yo me peino
tú te peinas
él/ella/usted se peina
nosotros/as nos peinamos
vosotros/as os peináis
ellos/ellas/ustedes se peinan

How would I say “My sister is doing her hair before leaving the house (right now)”?

Use the present progressive (estar + gerund) with the reflexive pronoun:

Mi hermana se está peinando antes de salir de casa.
or
Mi hermana está peinándose antes de salir de casa.

Both are correct. Note:

The reflexive pronoun (se) can go before the conjugated verb (está)
or attached to the gerund (peinándose).

Is peinarse always reflexive for personal grooming, like other verbs such as lavarse or ducharse?

Yes, for one’s own grooming, Spanish normally uses the reflexive forms:

lavarse = to wash oneself
- Me lavo las manos. = I wash my hands.
ducharse = to shower
- Se ducha por la mañana. = He/She showers in the morning.
afeitarse = to shave oneself
- Me afeito todos los días. = I shave every day.
peinarse = to comb/brush one’s hair
- Me peino antes de trabajar. = I do my hair before work.

When you groom someone else, you drop the reflexive pronoun and use a normal direct or indirect object:

Lavo a mi hijo. = I wash my son.
Ducho al bebé. = I shower the baby.
Peino a mi hermana pequeña. = I comb my little sister’s hair.