Mi hija quiere meterse en la piscina, pero hace frío.

Because mi without an accent is the possessive adjective meaning my.

• mi hija = my daughter

Mí with an accent is a pronoun meaning me after a preposition:

• para mí = for me
• sin mí = without me

So in this sentence, mi is correct because it is showing possession.

Spanish often leaves out subject pronouns when the verb already shows who the subject is.

• quiere already means he/she/it wants
• So Mi hija quiere... is perfectly clear

You could say Ella quiere meterse en la piscina, but it is usually unnecessary unless you want emphasis or contrast.

Quiere is the third person singular of querer, which means to want.

Here it agrees with mi hija, which is singular:

• yo quiero = I want
• tú quieres = you want
• él/ella quiere = he/she wants

So:

• Mi hija quiere... = My daughter wants...

Because meterse means to get oneself into, while meter by itself usually means to put something into something else.

Compare:

• meter el libro en la mochila = to put the book into the backpack
• meterse en la piscina = to get into the pool

The se shows that the subject is, in a sense, doing the action to themselves: getting herself into the pool.

Because after a conjugated verb like quiere, the next verb is usually in the infinitive, and reflexive pronouns can attach to that infinitive.

So:

• quiere meterse = wants to get in

This is the normal pattern:

• querer + infinitive
• querer + reflexive infinitive

You could not say quiere se meter in standard Spanish.

Both can mean to get into the pool, but meterse en la piscina often feels a bit more physical and natural in this context.

• entrar en la piscina = to enter the pool
• meterse en la piscina = to get into the pool / to go into the pool

In everyday speech, especially when talking about water, meterse en is very common. It can suggest actually going into the water, not just crossing the edge.

Because meterse is used with en, since the idea is movement into something.

• meterse en la piscina = to get into the pool

With some verbs of movement, Spanish uses a:

• ir a la piscina = to go to the pool

But here the meaning is not just going to the pool; it is going into the pool, so en is the natural choice.

Spanish uses the definite article much more often than English.

So even where English says:

• get into the pool

Spanish says:

• meterse en la piscina

This can refer to the specific pool in the situation, or just the pool understood from context. Using la here is completely normal.

Because hace frío is the standard Spanish expression for it’s cold when talking about the weather or general temperature conditions.

• Hace frío = It’s cold

Spanish often uses hacer with weather and temperature expressions:

• hace calor = it’s hot
• hace frío = it’s cold
• hace viento = it’s windy

Está frío usually means that something specific is cold, for example:

• El agua está fría = The water is cold
• La sopa está fría = The soup is cold

So in your sentence, hace frío means the weather/air is cold.

Because Spanish does not need a dummy subject like English it in weather expressions.

English says:

• It is cold

But Spanish simply says:

• Hace frío

There is no real subject there. English requires it, but Spanish does not.

Because pero means but, and it connects two clauses:

• Mi hija quiere meterse en la piscina
• pero hace frío

In Spanish, it is very common to put a comma before pero, especially when it links two complete ideas. This is similar to English punctuation with but.

Yes. That is also correct.

With a reflexive verb after a conjugated verb, the reflexive pronoun can often go in two places:

• Mi hija quiere meterse en la piscina
• Mi hija se quiere meter en la piscina

Both mean the same thing. The version with meterse attached to the infinitive is very common and often feels slightly cleaner in simple sentences like this.

Yes.

• hija = daughter
• The h is silent in Spanish

So hija is pronounced roughly like EE-ha, with the j being a strong Spanish sound, not like the English h or j.

Also, because hija is feminine singular, it matches naturally with mi and with the verb form quiere for she.

Usually it means to get into the pool, without necessarily specifying how.

Depending on context, it could mean:

• stepping in
• climbing in
• jumping in

If you want to be more specific:

• tirarse a la piscina = to dive / jump into the pool
• entrar en la piscina = to enter the pool
• meterse en la piscina = to get into the pool

So meterse is a broad, natural everyday choice.