Krvna pretraga je bila kratka, a moja kći je poslije hrabro popila vodu i sjela.

Both are possible, but they are built differently:

• krvna pretraga = literally blood test, using an adjective
• pretraga krvi = literally test/examination of blood, using a noun in the genitive

In everyday Croatian, krvna pretraga is a very natural fixed phrase for a blood test. English does something similar with noun modifiers, while Croatian often uses either:

• an adjective: krvna pretraga
• a genitive phrase: analiza krvi, pretraga krvi

So this is mostly a vocabulary/collocation point.

This is the Croatian past tense, built with:

• the present tense of biti (je = is/has as an auxiliary here)
• the past participle (bila)

So:

• je bila = was

The participle bila agrees with the subject:

• pretraga is feminine singular
• therefore the participle is bila (feminine singular)

Compare:

• test je bio = the test was
• pretraga je bila = the examination was
• djeca su bila = the children were

Because kratka is an adjective describing pretraga, which is feminine singular.

Agreement works like this:

• masculine singular: kratak
• feminine singular: kratka
• neuter singular: kratko
• plural forms vary too

Since pretraga is feminine, the predicate adjective must also be feminine:

• Pretraga je bila kratka.

If the noun were neuter, you would use kratko:

• Predavanje je bilo kratko. = The lecture was short.

A often links two clauses with a mild contrast or simply a shift to a new piece of information.

In this sentence:

• Krvna pretraga je bila kratka, a moja kći...

it feels like:

• The blood test was short, and/as for my daughter...
• or The blood test was short, and then my daughter...

It is not a strong contradiction like ali (but), and it is not just a simple additive i (and) either. Croatian a is very common when moving from one clause to another with a slight contrast, change of topic, or narrative progression.

Very roughly:

• i = and
• ali = but
• a = and/but/as for, depending on context

Yes, kći (daughter) is somewhat irregular and can feel unusual to learners.

In this sentence:

• moja kći = my daughter

Here kći is nominative singular, because it is the subject of the second clause.

A few useful forms:

• nominative: kći
• genitive: kćeri
• dative: kćeri
• accusative: kćer
• instrumental: kćeri / kćerju depending on style/usage

Also notice that moja agrees with kći in gender, number, and case.

Because je is a clitic, and Croatian clitics usually go in second position in the clause.

So in:

• moja kći je poslije hrabro popila vodu i sjela

the clitic je comes very early, after the first phrase moja kći.

This is a very important Croatian word-order rule. Clitics such as:

• sam, si, je, smo, ste, su
• se
• short pronouns like ga, joj, mi

generally do not go wherever you want. They tend to cluster near the beginning of the clause.

So moja kći je poslije... is the natural order.

Poslije means afterwards, later, or after that here.

In this sentence it works as an adverb of time:

• je poslije hrabro popila vodu = afterwards she bravely drank some water

It can also be used as a preposition with the genitive:

• poslije testa = after the test
• poslije škole = after school

So poslije can function in two ways:

1. Adverb: Poslije smo otišli kući. = Afterwards we went home.
2. Preposition: Poslije ručka... = After lunch...

Here it is the adverb use.

Because hrabro is an adverb, not an adjective.

It describes how she drank the water:

• hrabro popila = drank bravely

If you wanted to describe the daughter herself with an adjective, you would use:

• moja kći je hrabra = my daughter is brave

So compare:

• hrabra djevojčica = a brave girl (adjective)
• hrabro je popila vodu = she bravely drank the water (adverb)

Many Croatian adverbs are formed from adjectives, often with -o:

• brz → brzo
• hrabar → hrabro
• miran → mirno

The base verb is popiti, which is a perfective verb meaning to drink up, to drink, or to finish drinking in a completed sense.

In the past tense:

• masculine: popio
• feminine: popila
• neuter: popilo

Since moja kći is feminine, you get popila.

The perfective aspect matters here because the sentence presents the action as completed:

• popila vodu = she drank the water / she drank some water / she finished drinking the water

The related imperfective verb is piti:

• pila je vodu = she was drinking water / she drank water (focus less on completion)

So popila is a very natural choice when the event is seen as a completed action in a sequence.

Because voda is the direct object of popila, so it goes into the accusative singular:

• nominative: voda
• accusative: vodu

So:

• popila vodu = drank water

This is standard Croatian case use: direct objects normally take the accusative.

Compare:

• Vidim kuću. = I see the house.
• Imam knjigu. = I have a book.
• Popila je vodu. = She drank water.

Croatian does not have articles like English a/an/the.

So vodu can mean different things depending on context:

• the water
• some water
• just water

The listener figures it out from the situation.

In this sentence, English might translate it naturally as:

• she drank some water
• or she drank the water

Croatian leaves that unspecified unless the speaker adds other words for clarity.

Because sjela comes from sjesti, which means to sit down — a completed action of changing position.

So:

• sjela = sat down

By contrast, sjedila comes from sjediti, which means to be sitting or to sit in the sense of being in that position.

Compare:

• Sjela je na stolicu. = She sat down on the chair.
• Sjedila je na stolici. = She was sitting on the chair.

In your sentence, the meaning is a sequence of completed actions:

1. she drank water
2. she sat down

So sjela is exactly the right choice.

Because in coordinated verbs, Croatian can share the same auxiliary.

So:

• moja kći je poslije hrabro popila vodu i sjela

means:

• my daughter afterwards bravely drank water and sat down

The auxiliary je belongs to the whole coordinated verbal sequence. Croatian often avoids repeating it when it is obvious.

You could think of it as:

• je popila ... i (je) sjela

The second je is simply omitted because it is unnecessary.

Yes. In the Croatian past tense, the participle agrees with the subject in gender and number.

Since the subject is moja kći (feminine singular), you get:

• popila
• sjela

If the subject were masculine:

• moj sin je poslije hrabro popio vodu i sjeo

If plural feminine:

• moje kćeri su poslije hrabro popile vodu i sjele

So this is a very common agreement pattern in Croatian.

Yes, often you could.

For example:

• moja kći je nakon toga hrabro popila vodu i sjela

This means something like after that, my daughter bravely drank water and sat down.

But the nuance is a little different:

• poslije = afterwards / later
• nakon toga = after that, more explicitly tied to a previous event

In your sentence, poslije sounds very natural and compact.

Yes. It sounds like a normal, natural way to describe a short sequence of events in Croatian.

It has several common narrative features:

• past tense with je + participle
• perfective verbs for completed actions: popila, sjela
• clitic in second position: je
• adverb placement that sounds natural: poslije hrabro
• coordination with a and i

So it is a good example of everyday Croatian storytelling style.