Vestimos a la mujer para la fiesta.

This is the personal a. In Spanish, when the direct object is a specific person or other highly person-like being, you usually put a before it.

So in Vestimos a la mujer, la mujer is the direct object, and because she is a specific person, Spanish uses a.

Compare:

• Vestimos a la mujer = We dress the woman.
• Vestimos el maniquí = We dress the mannequin.

The a does not mean to here. It is just a grammatical marker for a personal direct object.

Vestimos is the first person plural present tense of vestir.

Here it means we dress or we are dressing, depending on context.

So:

• yo visto = I dress
• tú vistes = you dress
• él/ella viste = he/she dresses
• nosotros/nosotras vestimos = we dress
• ellos/ellas visten = they dress

In this sentence, vestimos means that we are putting clothes on someone else.

Usually, no—not in this sentence.

Vestir can sometimes relate to clothing in a broader sense, but in a sentence like Vestimos a la mujer, it clearly means to dress someone.

If you want to say we wear, Spanish more often uses:

• Llevamos ropa elegante = We wear elegant clothes.
• Estamos vestidos de negro = We are dressed in black.

So here, vestimos means we dress the woman, not we wear the woman or we wear clothes.

Because this sentence is about dressing another person, not getting dressed oneself.

There is an important difference:

• vestir a alguien = to dress someone
• vestirse = to get dressed / to dress oneself

Examples:

• Vestimos a la mujer = We dress the woman.
• La mujer se viste = The woman gets dressed.

So this sentence uses vestimos because the action is being done to the woman, not by the woman to herself.

La mujer is the direct object. She is the person receiving the action of vestimos.

The basic structure is:

• [subject] vestimos
• [direct object] a la mujer
• [purpose/context] para la fiesta

So:

• we = implied subject
• dress = verb
• the woman = direct object
• for the party = purpose or occasion

Spanish often leaves out subject pronouns because the verb ending already tells you who the subject is.

In vestimos, the ending -imos tells you the subject is we.

So Spanish usually says:

• Vestimos a la mujer para la fiesta.

Instead of:

• Nosotros vestimos a la mujer para la fiesta.

Adding nosotros is possible, but it is usually only done for emphasis, contrast, or clarity.

For example:

• Nosotros vestimos a la mujer, no ellos. = We dress the woman, not them.

Para la fiesta means for the party.

Here, para shows purpose, intended use, or occasion. It tells us why the woman is being dressed.

So the idea is:

• We dress the woman for the party
• We dress her so that she is ready for the party

This is a very common use of para.

Normally, no. Para is the natural choice here.

Why?

• para = for, in order for, intended for, for the purpose of
• por = because of, through, by, around, in exchange for, etc.

In this sentence, the party is the purpose/occasion, so para fits:

• Vestimos a la mujer para la fiesta = We dress the woman for the party.

If you used por la fiesta, it would sound more like because of the party, which is a different idea and not the normal phrasing here.

La mujer means the woman, so it refers to a specific woman that the speaker and listener can identify.

If you said:

• Vestimos a una mujer para la fiesta

that would mean We dress a woman for the party, which sounds less specific.

So the difference is:

• la mujer = a known/specific woman
• una mujer = any woman / an unspecified woman

Yes. The Spanish present tense often covers both ideas.

So Vestimos a la mujer para la fiesta can mean:

• We dress the woman for the party
  or
• We are dressing the woman for the party

The exact meaning depends on context.

If you want to make the ongoing action more explicit, Spanish can also use the progressive:

• Estamos vistiendo a la mujer para la fiesta.

But the simple present is very common and often enough.

Yes. Since la mujer is a feminine singular direct object, you can replace it with la.

So:

• Vestimos a la mujer para la fiesta. becomes
• La vestimos para la fiesta.

This means We dress her for the party or We are dressing her for the party.

Notice that when you use the pronoun la, you do not keep a la mujer unless you are adding it for clarification:

• La vestimos a ella para la fiesta.
  This is possible, but more emphatic or clarifying.

It is stem-changing in many forms, so learners usually treat it as an irregular pattern.

The infinitive is vestir, but the stem changes from e to i in many present-tense forms:

• yo visto
• tú vistes
• él/ella viste
• nosotros vestimos
• ellos/ellas visten

Notice that nosotros vestimos does not have the stem change. This is very common with this kind of verb.

So learners often notice:

• viste, visten but
• vestimos

That pattern is normal.

That would be a different structure.

• Vestimos a la mujer para la fiesta = We dress the woman for the party.
• Vestimos a la mujer de rojo = We dress the woman in red.
• Vestimos a la mujer de princesa = We dress the woman as a princess.

So:

• para la fiesta tells you the purpose/occasion
• de rojo / de princesa tells you the style, color, or costume

You can even combine them:

• Vestimos a la mujer de rojo para la fiesta. = We dress the woman in red for the party.