Вчера я купила белую блузку, а к ней маленькую сумочку.

Because the verb is in the past tense, and in Russian past tense verbs agree with the speaker’s gender in the singular.

• я купил = I bought (said by a man)
• я купила = I bought (said by a woman)

So this sentence is being said by a female speaker.

Also, купила is from купить, which is perfective. That means it presents the action as completed: I bought / I did buy.

Because they are in the accusative case, since they are the direct object of купила.

The dictionary forms are:

• белая = white
• блузка = blouse

But after купила (bought), you need the thing bought in the accusative:

• белая блузка → белую блузку

This is the normal pattern for a feminine singular inanimate noun with its adjective:

• nominative: белая блузка
• accusative: белую блузку

Russian often leaves out a verb when it is easily understood from the previous part of the sentence.

So:

• Вчера я купила белую блузку, а к ней маленькую сумочку.

really means:

• Вчера я купила белую блузку, а к ней (купила) маленькую сумочку.

In natural English, that would be something like:

• Yesterday I bought a white blouse, and a small handbag to go with it.

This omission is very natural in Russian and helps avoid repetition.

Not exactly. Although а is often translated as but, here it is closer to:

• and
• while
• and as for
• and also

It links two related pieces of information, often with a slight contrast or shift of focus.

Here the idea is:

• I bought a white blouse, and for it / to go with it, a small handbag.

So in this sentence, а does not sound strongly adversative like English but.

Literally, к usually means to / toward, but in this kind of sentence к ней means something like:

• for it
• to go with it
• to match it

So:

• блузку, а к ней маленькую сумочку

means:

• a blouse, and a small handbag to go with it

This is a very common Russian pattern:

• купить платье и к нему туфли = to buy a dress and shoes to go with it
• выбрать шторы и к ним ковёр = to choose curtains and a rug to match

Because the preposition к requires the dative case.

The pronoun она changes by case:

• nominative: она = she / it
• genitive/accusative: её
• dative: ей

But after some prepositions, Russian uses a form with н-:

• к ней = to her / to it

So:

• к ней is the correct form after к
• it refers here to блузке (the blouse), which is feminine

This н- appears in many prepositional combinations:

• у неё
• с ней
• для неё
• к ней

Because it is also a direct object of the understood verb купила.

Even though the verb is omitted, it is still felt in the sentence:

• (купила) маленькую сумочку

So both words take accusative feminine singular forms:

• маленькая сумочка → маленькую сумочку

This matches the first object pattern:

• белую блузку
• маленькую сумочку

Сумочка is a diminutive form of сумка.

Very roughly:

• сумка = bag
• сумочка = little bag / handbag

But diminutives in Russian do more than just mean small. They can also sound:

• more affectionate
• softer
• more natural in everyday speech
• more specific to a feminine accessory like a handbag

So in this sentence, сумочка sounds very natural if the speaker means a small handbag or a nice little bag to match the blouse.

Russian word order is flexible, and word order often shows focus rather than basic grammar.

By saying:

• а к ней маленькую сумочку

the speaker emphasizes the idea to go with it first. The sentence is structured around the matching relationship:

• first the blouse
• then the item chosen to go with the blouse

If you changed the order, the meaning would stay similar, but the emphasis would shift.

So this version sounds natural because it highlights the idea:

• and to go with it, a small handbag

No. Вчера means yesterday, and it is an adverb of time. It does not require any special case after it.

It simply sets the time for the whole sentence:

• Вчера я купила... = Yesterday I bought...

So the cases in the sentence are determined by other things:

• купила → accusative objects
• к → dative pronoun

Yes, it is natural, especially in conversational or everyday Russian.

It sounds slightly elliptical, because the second купила is omitted, but that is very common. A fuller version would be:

• Вчера я купила белую блузку, а к ней купила маленькую сумочку.

A speaker might also say:

• Вчера я купила белую блузку и к ней маленькую сумочку.
• Вчера я купила белую блузку, а к ней ещё маленькую сумочку.

But your original sentence is completely normal and idiomatic.