Ona se ne želi presvući prije sastanka, jer kaže da joj ta suknja i kapa dobro stoje.

Yes. Croatian often leaves out subject pronouns because the verb already shows person and number.

• Ne želi se presvući prije sastanka... is perfectly possible.
• Ona is included for emphasis, contrast, or clarity.

So ona here can mean something like she, specifically or simply make the subject clearer in context.

Because the verb is presvući se, a reflexive verb meaning to get changed / change clothes.

In Croatian, many verbs use se where English does not use a separate word.

• presvući se = to change clothes
• presvući dijete = to change a child’s clothes
• presvući krevet = to change the bed linen

So se shows that she is changing herself, not someone or something else.

This is because se is a clitic, and Croatian clitics usually appear near the beginning of the clause, often in second position.

So even though se belongs in meaning with presvući se, it can move up in front of the finite verb:

• Ona se ne želi presvući = natural
• Ona ne želi se presvući = not standard/natural

Also notice that ne stays directly in front of želi, because Croatian negation normally goes immediately before the finite verb.

They are related, but not the same.

• obući se = to get dressed, to put clothes on
• presvući se = to change clothes, to change into something else

So this sentence suggests she is already dressed, but does not want to switch to a different outfit before the meeting.

Because presvući se is perfective, and here the idea is a single complete action:

• changing clothes once
• before the meeting

That makes the perfective verb natural.

Compare:

• želi se presvući = she wants to get changed once
• želi se presvlačiti = she wants to be changing clothes / change clothes repeatedly / in an ongoing sense

In this sentence, the complete one-time action is what matters.

Because prije requires the genitive case.

The noun sastanak becomes sastanka in the genitive singular:

• sastanak = meeting
• prije sastanka = before the meeting

This is a very common pattern in Croatian:

• prije škole = before school
• prije ručka = before lunch
• prije puta = before the trip

Here da introduces a subordinate clause, like English that:

• kaže da joj ta suknja i kapa dobro stoje
• she says that that skirt and hat look good on her

In English, that is often optional. In Croatian, da is very commonly used in this kind of sentence.

Joj is the dative singular form of ona.

Here it means to her / on her, because the verb stajati in this meaning takes the dative:

• To joj dobro stoji = That looks good on her
• Te cipele joj ne stoje dobro = Those shoes do not suit her / do not look good on her

So joj is not a direct object. It is a dative form connected with the idea of how something looks on someone.

It is the unstressed clitic form. The stressed form is njoj.

That is a very common extended meaning of stajati in Croatian, especially with clothing.

With clothes, stajati often means:

• to suit someone
• to look good on someone
• to fit someone aesthetically

Examples:

• Ta haljina joj dobro stoji. = That dress looks good on her.
• Crvena ti ne stoji baš najbolje. = Red does not suit you very well.

So in this sentence, ta suknja i kapa dobro stoje means the skirt and hat look good on her, not that they are physically standing somewhere.

Because the subject is plural: ta suknja i kapa.

Even though the two nouns are linked by i and only one ta appears, together they form a compound subject, so the verb must be plural:

• suknja stoji = the skirt looks good
• kapa stoji = the hat looks good
• suknja i kapa stoje = the skirt and hat look good

Because dobro is an adverb, and it modifies the verb stoje.

It tells us how they look on her:

• dobro stoje = they look good

If you used dobra/dobri/dobre, those would be adjectives describing nouns, not the action or result expressed by the verb.

So here Croatian works like English:

• look good
• not look good ones

Croatian can use one demonstrative for a coordinated phrase when the speaker treats the items as one set.

So ta suknja i kapa can mean roughly that skirt and hat.

You can also repeat it:

• ta suknja i ta kapa

Repeating ta makes each item more individually marked. Using it once is a little lighter and very natural in context.

Also remember that Croatian has no articles, so ta helps point to specific known items, somewhat like that in English.