Я купила маленькую сумочку к светлой блузке.

Because the speaker is female.

In the past tense, Russian verbs agree with the subject in gender and number:

• купил = he bought / I bought if the speaker is male
• купила = she bought / I bought if the speaker is female
• купило = neuter
• купили = plural

So Я купила tells us that the person saying this is a woman.

Because it is the direct object of the verb купила, so it has to be in the accusative case.

The dictionary form is:

• сумочка = handbag, little bag

But after купить (to buy), we ask what did she buy? The answer is the object, so we use the accusative:

• сумочка → сумочку

This is a very common pattern for feminine nouns ending in -а / -я:

• книга → книгу
• машина → машину
• сумочка → сумочку

Because the adjective has to agree with сумочку in gender, number, and case.

Since сумочку is:

• feminine
• singular
• accusative

the adjective must match it:

• маленькая сумочка = nominative
• маленькую сумочку = accusative

So the ending changes from -ая to -ую.

This is standard adjective agreement in Russian.

Here к means something like to go with, to match, or for in the sense of choosing one item to suit another.

So:

• сумочку к светлой блузке = a handbag to go with a light-colored blouse

This is a very common use of к with clothes, accessories, furniture, colors, and similar things:

• галстук к рубашке = a tie to go with a shirt
• туфли к платью = shoes to go with a dress

So this is not literal movement toward something. It is more about matching.

Because the preposition к requires the dative case.

The noun блузка is feminine singular, and in the dative it becomes:

• блузка → блузке

The adjective must also agree with it in the dative:

• светлая блузка = nominative
• светлой блузке = dative

So after к, both words change:

• к светлой блузке

This is something you simply have to learn with the preposition:

• к + dative

Сумочка is a diminutive form of сумка.

• сумка = bag
• сумочка = little bag, handbag, or a more affectionate/softer way to say it

Diminutives in Russian can show:

• small size
• affection
• something neat, cute, or elegant
• a lighter, less formal tone

So сумочка often sounds more like handbag or cute little bag than the more general сумка.

Not necessarily.

It is true that сумочка already has a diminutive feel, so it can suggest a smaller or more delicate kind of bag. But маленькую adds an extra, more literal emphasis on size.

So the phrase can suggest:

• a genuinely small handbag
• a small, neat accessory
• a stylistic choice in description

Russian often allows this kind of overlap. It does not sound wrong.

Yes. Here светлой means light-colored.

The base form is:

• светлый = light, pale, light-colored

With блузке in feminine singular dative, it becomes:

• светлой

So светлая блузка means a light blouse or more naturally a light-colored blouse.

In clothing contexts, светлый usually refers to color or shade, not to brightness in the sense of emitting light.

Yes, Russian word order is fairly flexible.

The neutral order here is:

• Я купила маленькую сумочку к светлой блузке.

This sounds natural and straightforward.

But other orders are possible if you want to emphasize something:

• Маленькую сумочку я купила к светлой блузке.
  Emphasis on the handbag
• К светлой блузке я купила маленькую сумочку.
  Emphasis on the blouse as the reference item

Even though word order can change, the case endings still show the grammatical relationships, so the meaning stays clear.

Купила is the perfective past tense of купить, and it presents the action as completed: she bought it, and the result matters.

That is the normal choice here, because the sentence is about a finished purchase.

• Я купила маленькую сумочку... = I bought a small handbag...

If you said покупала instead, that would be the imperfective verb покупать, which usually focuses more on the process, repetition, or background context:

• Я покупала маленькую сумочку... could mean something like I was buying / used to buy / went to buy

In this sentence, купила is the natural form because it refers to one completed act.

Yes, often it can.

Russian frequently leaves out subject pronouns when they are clear from the verb form or the context:

• Купила маленькую сумочку к светлой блузке.

This can still mean I bought a small handbag to go with a light blouse, especially if the speaker is already understood.

However, Я is perfectly natural too. It may be included for clarity, contrast, or simple conversational style.