Learn Hardcore Japanese: kanozyo ha hito ga ooi tokoro ga nigate da ga, siten no tetudai ni itta. - She’s not good with crowds, but she went to help at the branch.

In 人が多い, が marks the subject of the relative clause that modifies ところ (places where “people are many” = crowded places).
In X が苦手だ, が marks the thing someone is bad at/uncomfortable with. Here, 人が多いところ is that X. So: 彼女は [人が多い] ところが苦手だ.

Is ところが here the conjunction meaning “however”?

No. It’s not the standalone conjunction ところが (“however”). It’s ところ + が where が marks “the thing one is bad at” in the pattern X が苦手だ. The sentence’s “but” is the だが later on.

Why use は on 彼女 but が on ところ?

は marks the topic (what we’re talking about): 彼女は. が in X が苦手だ marks the specific thing she’s not good with: 人が多いところ. This pattern—topic with は + disliked/weak-at thing with が—is very common: 私は犬が苦手です.

Could I say 人の多いところ instead of 人が多いところ?

Yes. In relative clauses, の can often replace が as a subject/possessor marker: 人の多いところ ≈ 人が多いところ. Both are natural; が is a bit more neutral; の can feel slightly more attributive/written, but the difference is small here.

Why ところ instead of 場所?

Both can mean “place,” but:

ところ is broader and can mean “kind of place/situation,” so 人が多いところ naturally means “crowded places (in general).”
場所 is more concrete/physical. 人が多い場所 is also fine, just a shade more concrete/formal.

What exactly does 苦手 mean here? Is it “dislike” or “bad at”?

苦手 means “not good with/poor at/uncomfortable with.” It can include mild dislike or discomfort. It’s softer and broader than:

きらい (dislike/hate: strong preference)
下手 (unskilled: ability-focused) With places/crowds, 苦手 implies “crowds aren’t her thing; she doesn’t handle them well.”

What is だが doing, and how is it different from が, けど, けれども?

だが is “but/however,” attaching to the predicate 苦手だ. Style differences:

だが: written/formal.
が (conjunctive): neutral/formal-ish (e.g., 苦手だが、…).
けど／けれども: more conversational (politer/longer with けれども).
ですが: polite. All mean “but,” with differing formality.

Is the が in だが the same as the subject marker が?

No. In だが, が is a conjunction meaning “but.” It does not mark a subject.

How does 手伝いに行った work? Why に?

It’s the purpose construction V-ます stem + に + 行く = “go in order to V.”

手伝う → ます-stem 手伝い
手伝いに行った = “went to help (out).” The に here marks purpose, not destination.

Why 支店の手伝いに行った and not 支店を手伝いに行った?

Both are possible, with a nuance difference:

支店の手伝いに行った: treats 手伝い as a noun (“helping-out work”) for the branch; “went to do help for/at the branch.”
支店を手伝いに行った: treats 支店 as the direct object of 手伝う; “went to help the branch.” Both are idiomatic. Using の focuses on the task; using を focuses on the target you help.

If に marks purpose, how do I show the destination (to the branch)?

You can add a separate destination:

支店に手伝いに行った (destination に + purpose に)
Or split it: 支店に行って、手伝った。 The original sentence implies helping at a branch without explicitly marking the destination.

Could I replace だが with だけど or ですが?

Yes, with style changes:

苦手だけど、…: more casual/conversational.
苦手ですが、…: polite. Choose based on the formality you want.

Why is the sentence in plain form (だ / 行った) instead of polite?

It’s a stylistic choice. Plain form is common in narration, writing, or casual contexts. Polite equivalents: 苦手ですが、支店の手伝いに行きました。

Can I drop 彼女は or move parts around?

Yes:

Dropping the topic is fine if it’s clear from context: 人が多いところが苦手だが、支店の手伝いに行った。
You can topicalize the place: 人が多いところは苦手だが、… (then you often omit 彼女は to avoid double topics).

Any kanji notes for ところ?

ところ can be written 所, but the kana form ところ is very common in general text. Either is acceptable here: 人が多いところ／所.