Learn Hardcore German: Ihre Bluse ist neu, aber sie passt überhaupt nicht zu dieser Hose. - Her blouse is new, but it does not go with these pants at all.

her (possessive of “she”: lowercase ihre, but it’s capitalized here only because it starts the sentence), or
formal your (possessive of the polite Sie, always written with capital I: Ihre).

From this sentence alone, both “Her blouse …” and “Your blouse (formal) …” are possible. The following sie refers to the blouse, not to a person.

Why is it sie passt and not es passt?

Because Bluse is feminine in German (die Bluse). Pronouns agree with grammatical gender, so you use sie (“she/it” for feminine nouns). For a neuter noun like das Hemd you’d say es passt, and for a masculine noun like der Rock you’d say er passt.

What does passen zu mean, and why not use mit?

With clothes, passen zu (+ dative) means “to go with/match.” You don’t use mit for this meaning. Examples:

Die Bluse passt zu der Hose. = The blouse goes with the trousers.
Using mit would suggest physical accompaniment (“with”) rather than the idiomatic “matches.” Stick to passen zu.

Why is it zu dieser Hose (dative) and why the ending -er on dieser?

The preposition zu always takes the dative case. Hose is feminine, and the dative feminine form of the demonstrative is dieser. Compare:

Feminine: zu dieser Hose
Masculine: zu diesem Rock
Neuter: zu diesem Hemd
Plural: zu diesen Schuhen

Can I say zur Hose instead of zu der Hose? What about with dieser?

Yes, zu der Hose can contract to zur Hose. But contraction only works with the definite article. You cannot contract with a demonstrative, so don’t say “zur dieser Hose.” Keep zu dieser Hose.

What does überhaupt nicht add compared to just nicht? Is gar nicht the same?

überhaupt nicht intensifies the negation: “not at all.” gar nicht is a very common near‑synonym. Plain nicht is less emphatic.

Sie passt nicht zu dieser Hose. = It doesn’t go with these trousers.
Sie passt überhaupt/gar nicht zu dieser Hose. = It doesn’t go with them at all.

Can I move (überhaupt) nicht to the end: Sie passt zu dieser Hose überhaupt nicht?

Yes. Both are grammatical, but the focus shifts:

Sie passt überhaupt nicht zu dieser Hose. Neutral emphasis; general strong negation.
Sie passt zu dieser Hose überhaupt nicht. Puts extra focus on the prepositional phrase (“… to these trousers it really doesn’t match,” possibly implying it might match something else).

Why is it ist neu and not ist neue?

After the verb “to be,” adjectives are predicative and take no ending: ist neu. Endings appear only when the adjective directly modifies a noun (attributive):

Predicative: Ihre Bluse ist neu.
Attributive: Ihre neue Bluse ist schön.

Do I need the comma before aber, and what’s the word order after it?

Yes, the comma is required here because two independent clauses are joined. aber is a coordinating conjunction, and the second clause keeps normal main‑clause word order (finite verb in the second position):

Correct: …, aber sie passt …
Not in one sentence: …, aber passt sie … (that inversion would work only in a separate exclamatory sentence: Aber passt sie überhaupt nicht!)

Could I use doch instead of aber? What about sondern?

doch can replace aber with a similar “but/however” meaning, slightly more formal/literary: …, doch sie passt …
sondern means “but rather” and is used only after a negation that is being corrected: Nicht X, sondern Y. It doesn’t fit here.

Why is Hose singular in German when English uses plural “trousers/pants”?

German treats a single pair as singular: die Hose. Plural is die Hosen for multiple pairs.

One pair: eine Hose
Two pairs: zwei Hosen

What’s the difference between passen, passen zu, and jemandem stehen?

passen (+ Dativperson) = to fit in size: Die Bluse passt mir nicht.
passen zu (+ Dativsache/Person) = to go with/match: Die Bluse passt zu der Hose.
jemandem stehen = to suit (look good on someone): Die Bluse steht dir.

Is the lowercase sie ever the formal “you” here?

No. The formal “you” is capitalized (Sie) and takes the verb form like plural: Sie passen. Here we have lowercase sie with passt (3rd person singular), so it clearly refers to the feminine noun Bluse (“it”), not to a person.

Why does the possessive have the form Ihre here? Would it change with other nouns?

Possessive determiners (like ihr-/Ihr-) inflect like “ein‑words.” With a feminine noun in the nominative, you add -e: Ihre Bluse. Other examples:

Masculine nominative: Ihr Rock (no ending on Ihr)
Neuter nominative: Ihr Kleid
Plural nominative: Ihre Schuhe

Are there natural alternatives to say the same thing?

Yes:

Ihre Bluse ist neu, aber sie passt gar nicht zu dieser Hose.
Ihre Bluse ist neu, aber sie passt überhaupt nicht dazu. (if “that” item is clear from context)
Die Bluse und die Hose passen überhaupt nicht zusammen. (they don’t go together at all)