Learn Hardcore German: Sie hat mir leider nicht helfen können, aber ihr Rat war deutlich. - Unfortunately she was not able to help me, but her advice was clear.

Context decides. Here it’s most likely she, because later we see ihr Rat with a lowercase ihr = “her.” If it were formal “your,” it would be capitalized: Ihr Rat. Note that sentence-initial Sie is always capital, so it alone doesn’t disambiguate.

Why mir and not mich after helfen?

Because helfen governs the dative: jemandem helfen. Hence mir (to me), not mich (me). Other common dative verbs include danken, folgen, glauben, gefallen, passen, vertrauen.

What’s going on with hat … nicht helfen können (double infinitive at the end)?

It’s the Perfekt (present perfect) of a modal verb:

Finite auxiliary in position 2: hat
Both infinitives at the end (the “right bracket”): full verb first (helfen), modal second (können)
Negation in the midfield: nicht This yields the standard order: Sie hat mir leider nicht helfen können.

Can I simply say Sie konnte mir leider nicht helfen instead?

Yes. That’s Präteritum (simple past) and is very common—often preferred in speech for modal verbs. Both versions are correct; choose based on style/region/context.

Why is there no zu before helfen?

Modal verbs (like können, müssen, dürfen, wollen, sollen, mögen) take a bare infinitive: kann helfen (not kann zu helfen). Even in the double-infinitive Perfekt, there’s no zu: hat … helfen können. With non-modals you’d use zu, e.g., Sie hat versucht, mir zu helfen.

Why is nicht placed before helfen?

Because it negates the action of helping. General pattern: place nicht before the infinitive (or before a separable prefix). Compare:

Affirmative: Sie konnte mir helfen.
Negative: Sie konnte mir nicht helfen. Putting nicht elsewhere can sound wrong or change scope.

Could I move leider elsewhere in the clause?

Yes. Common placements:

Leider hat sie mir nicht helfen können.
Sie hat mir leider nicht helfen können. Both are natural. Unstressed pronouns like mir usually appear early in the midfield; sentence adverbs like leider often come after them.

Why is there a comma before aber, and why doesn’t the verb go to the end after it?

The comma is required because aber links two independent main clauses.
Aber is a coordinating conjunction, not subordinating. So the second clause keeps normal main-clause word order (verb in position 2): … aber ihr Rat war deutlich.

What nuance does deutlich have here? How is it different from klar, eindeutig, or offensichtlich?

deutlich: clear, easy to understand, explicit (e.g., clearly phrased advice)
klar: clear/understandable in a broad sense; very common and neutral
eindeutig: unambiguous, leaving no room for interpretation
offensichtlich: obvious/apparent (often about facts, not phrasing) Here, ihr Rat war deutlich ≈ her advice was clearly expressed.

What exactly is Rat here? Is it countable? How about plurals?

Rat = advice (uncountable in English). German allows:

der Rat (advice in general)
ein Rat (a piece of advice), but more idiomatic is ein Ratschlag
Plural for “pieces of advice”: Ratschläge Be careful: Räte is the plural of “council/councillor,” not advice.

Why no article in ihr Rat?

Possessive determiners (mein, dein, sein, ihr, unser, euer, Ihr) replace the article: ihr Rat = “her advice.” You wouldn’t add der here.

What are the case and agreement in aber ihr Rat war deutlich?

Rat is nominative singular (subject).
ihr is the possessive determiner; its form reflects the possessed noun (masc. nom. sg. → no ending: ihr Rat). With other cases you’d see endings: ihren Rat (acc.), ihrem Rat (dat.).
war agrees with Rat (3rd person singular).
deutlich is a predicative adjective, so no ending.

Which auxiliary do modals use in the Perfekt—haben or sein?

Modals take haben in the Perfekt, even if the accompanying full verb would normally take sein. Example: Er hat nach Hause gehen müssen (not: ✗ist … gehen müssen).

Could I say Sie hat mir nicht helfen gekonnt using gekonnt?

In Standard German with a full verb, prefer the double-infinitive: … nicht helfen können. Forms like … helfen gekonnt occur regionally or in older styles but are often marked in formal writing. You can use gekonnt if the modal stands alone: Sie hat es nicht gekonnt (“She wasn’t able to do it”).

How would I say she wasn’t allowed or didn’t want to help (not just couldn’t)?

Not allowed: Sie durfte mir leider nicht helfen.
Didn’t want to: Sie wollte mir leider nicht helfen.
Didn’t manage (result): Sie hat mir leider nicht helfen können. Each modal changes the reason for the non-help.