Mi prima salió del vestuario con una sonrisa y dijo que nunca había vivido un partido tan intenso.

Mi prima means my female cousin. Spanish distinguishes gender here:

• primo = male cousin
• prima = female cousin

So mi prima tells you the cousin is female.

Salió is the preterite form of salir and refers to a completed action in the past: she went out / came out of the changing room.

• salió = she went out / came out
• salía = she was going out / used to go out

Here, the sentence is narrating a specific event, so salió is the natural choice.

The accent in salió shows both pronunciation and distinguishes the form.

It is pronounced roughly sa-LEE-o. The accent tells you the stress falls on the final syllable of the verb form.

Also, salio without an accent would be incorrect in standard Spanish.

Del is the contraction of de + el:

• de = from / of
• el = the
• del = from the / of the

So:

• del vestuario = from the changing room / locker room

This contraction is required in Spanish when de is followed by el.

Here, vestuario means changing room or locker room.

In a sports context in Spain, vestuario is very commonly used for the room where players change clothes before or after a match.

It can also mean costumes/wardrobe in other contexts, but here the sports meaning is the right one.

Con una sonrisa literally means with a smile. It is a very natural way in Spanish to describe someone’s expression or manner.

So:

• salió del vestuario con una sonrisa = she came out of the changing room with a smile

Spanish could also use sonriendo (smiling), but con una sonrisa sounds slightly more descriptive and idiomatic in many contexts.

Dijo is the preterite of decir, meaning she said. It presents what she said as a completed event in the story.

• dijo = she said
• decía = she was saying / used to say

Since the sentence is telling us about one specific moment when she spoke, dijo is the correct choice.

After verbs like decir, Spanish normally uses que to introduce reported speech:

• dijo que... = she said that...

English can sometimes omit that:

• She said she had never experienced...

But in Spanish, que is usually kept:

• Dijo que nunca había vivido...

Había vivido is the pluperfect (also called the past perfect) of vivir.

It is formed with:

• había (imperfect of haber)
• vivido (past participle of vivir)

So:

• había vivido = had lived / had experienced

It is used here because her experience of never having lived/experienced such an intense match is presented as something that existed before the moment when she said it.

In English, this is also very natural:

• She said that she had never experienced such an intense match.

Yes, vivir usually means to live, but it can also mean to experience something emotionally or personally.

So in this sentence:

• haber vivido un partido = to have experienced a match

This is a very common Spanish usage, especially when talking about strong events, emotions, or situations.

A literal translation like had never lived a match sounds strange in English, but in Spanish it is completely natural.

Both are possible, but nunca había vivido is very natural and common.

Spanish often places nunca before the verb:

• nunca había vivido = had never experienced

You may also hear:

• no había vivido nunca

Both mean the same thing. The version in your sentence is simply a very normal word order.

Tan is used in comparisons or in structures meaning so / such.

Here:

• un partido tan intenso = such an intense match / so intense a match

By contrast:

• muy intenso = very intense

So:

• un partido muy intenso = a very intense match
• un partido tan intenso = such an intense match

Because the sentence is expressing an extreme degree in relation to everything she had experienced before, tan is the better choice.

The normal word order in Spanish is:

• un partido tan intenso

That is:

• article + noun + degree word + adjective

So:

• un partido = a match
• tan intenso = so intense / such an intense one

Placing it as tan intenso un partido would sound unnatural here.

No. Although partido can have different meanings in Spanish, here it clearly means match or game, especially because of the sports context created by vestuario.

Common meanings of partido include:

• match/game (sports)
• political party
• split/divided in other contexts

Here, vestuario + partido strongly points to sports.

The personal a is generally used with specific people (and sometimes pets or personified beings), not with things.

So:

• vivió un partido = correct
• no personal a, because un partido is a thing, not a person

Compare:

• Vi a mi prima = I saw my cousin
• Vivió un partido increíble = She experienced an incredible match

Yes, one clue is vestuario, which is very common in Spain for changing room / locker room, especially in sports.

Learners may also notice that the whole sentence sounds very natural in Spain-style sports narration:

• salió del vestuario
• vivir un partido
• un partido tan intenso

These are all very idiomatic in Spanish from Spain, though much of the sentence would also be understood elsewhere in the Spanish-speaking world.