Rekla je da će doći otprilike u sedam, ali je stigla nekoliko minuta ranije.

Croatian often leaves out subject pronouns when they are clear from the verb form and context.
Here, rekla is feminine singular, so the sentence already tells you the subject is she.

• Rekla je = normal, natural
• Ona je rekla = more explicit, often used for emphasis or contrast

So the omitted ona is understood.

Both are past-tense forms that agree with the subject in gender and number.

• rekla = feminine singular
• stigla = feminine singular

That tells you the speaker is talking about a female person.
If it were a man, you would have:

• Rekao je da će doći... ali je stigao...

After verbs like reći meaning to say, Croatian normally keeps the future tense in the subordinate clause if the action was still in the future at that time.

So:

• Rekla je da će doći = literally She said that she will come
• natural English translation = She said that she would come

English usually shifts will to would after a past reporting verb, but Croatian usually does not do that kind of tense backshifting here.

Da bi došla would mean something different. It usually introduces purpose or a more conditional meaning, not ordinary reported speech.

This is the Croatian future I tense:

• će = auxiliary
• doći = infinitive

Together, će doći means will come.

With other persons, you get forms like:

• doći ću = I will come
• doći će = she/he will come
• doći ćemo = we will come

In this sentence, because of clitic word order, it appears as da će doći.

Because the normal future tense in Croatian uses the auxiliary ću/će/ćemo plus the infinitive.

So:

• će doći = will come

not

• će došla ✘

The form došla is a past participle-like form used in the past tense, for example:

• Došla je u sedam = She came at seven

Je is a clitic, and Croatian clitics usually go in the second position in their clause.

So:

• Rekla je...
  The first main word is Rekla, so je comes right after it.

• ali je stigla...
  The clause begins with ali, so the clitic je comes right after ali.

This second-position behavior is very important in Croatian word order.

Yes, they are close in meaning, but they are not exactly identical.

• doći = to come, to arrive
• stići = to arrive, to reach, to get somewhere

In this sentence:

• da će doći focuses on the expected coming
• stigla focuses on the actual arrival

Using both in one sentence sounds natural in Croatian. English often repeats come, but Croatian can vary the verb more comfortably here.

Otprilike means approximately, roughly, or about.

Here:

• otprilike u sedam = approximately at seven / about seven o’clock

Its position is fairly flexible, but this placement is very natural. For example, these are also possible in some contexts:

• Rekla je da će doći u sedam otprilike
• Rekla je da će otprilike doći u sedam

Still, otprilike u sedam is a very common and smooth choice.

Croatian uses u with clock times to mean at a certain time:

• u jedan = at one
• u pet = at five
• u sedam = at seven

So u sedam means at seven o’clock.

This is just the normal Croatian pattern for specific times on the clock.

With clock time, u normally takes the accusative.

In u sedam, the numeral sedam does not visibly change, so you do not see a special ending here. But functionally, this is the standard time expression used with u + accusative.

For a learner, the most practical thing is simply to remember:

• u + time = at that time

Because nekoliko usually requires the genitive plural of the noun.

So:

• nekoliko minuta = several minutes
• nekoliko dana = several days
• nekoliko ljudi = several people

That is why the noun appears as minuta here.

Ranije means earlier. It is the comparative adverb of rano meaning early.

So:

• rano = early
• ranije = earlier

Croatian very naturally uses this comparative form when something happened earlier than expected, earlier than planned, or earlier than some reference point.

In this sentence, the reference point is otprilike u sedam, so:

• stigla nekoliko minuta ranije = she arrived a few minutes earlier

Yes, you could, and it would be understandable. But ranije is especially natural here because it directly means earlier in relation to the expected time.

Compare:

• nekoliko minuta ranije = a few minutes earlier
• nekoliko minuta prije = a few minutes before

Both can work, but ranije sounds very natural when comparing the actual arrival with the expected arrival time.

Because ali means but and joins two contrasting clauses. In standard Croatian punctuation, a comma is normally used before ali in this kind of sentence.

So the structure is:

• Rekla je da će doći otprilike u sedam,
• ali je stigla nekoliko minuta ranije.

The comma marks the contrast between expectation and reality.

Both doći and stići are perfective verbs. That means they refer to a completed event:

• doći = to come, to arrive as a completed act
• stići = to arrive, to reach as a completed act

That fits this sentence well because both actions are seen as whole events:

• the expected arrival
• the actual arrival

If you wanted a habitual or ongoing sense, Croatian would more likely use imperfective partners such as dolaziti or stizati, depending on the context.

You would change the past-tense forms to masculine:

• Rekao je da će doći otprilike u sedam, ali je stigao nekoliko minuta ranije.

Only the past-tense forms change here:

• rekla → rekao
• stigla → stigao

The rest stays the same.