Learn Hardcore Japanese: watasi ha genkin wo yoku tukau ga, kanozyo ha genkinigai mo tukau. - I often use cash, but she also uses things other than cash.

は marks the topic. Here it sets up a contrast: 私は…が、彼女は… = “As for me … but as for her ….” It’s not a pure subject marker (that’s typically が); it highlights what you’re talking about and often carries a contrastive nuance in this pattern.

Is the が here the subject marker or does it mean “but”? Why the comma?

Here が is the conjunction meaning “but/however,” linking two clauses. The comma 、 marks a natural pause and is common before conjunctive が in writing. It’s not the subject-marking が in this sentence.

What does よく mean here, and where can it go?

よく means “often/frequently” here (not “well”). Placement:

私は現金をよく使う and 私はよく現金を使う are both natural.
The first slightly emphasizes the action “use,” the second slightly emphasizes the frequency, but the difference is small.

Why 現金を使う and not 現金で使う? How do I say “pay in cash”?

With 使う (“to use”), the thing you use takes を: 現金を使う, カードを使う.
With 払う/支払う (“to pay”), the means takes で: 現金で払う, カードで払う.
Both are natural depending on the verb you choose.

In 現金以外も使う, where did the を go? Is it okay to drop it?

も can replace other particles like を/が. So 現金以外も使う = “(She) also uses things other than cash,” with も standing where を would have gone. This is standard.

Do I need の or もの after 以外? Is 現金以外も使う missing something?

It’s an acceptable ellipsis. More explicit versions are:

現金以外のものも使う (“uses things other than cash, too”)
現金以外の支払い方法も使う (“uses payment methods other than cash, too”) Conversational Japanese often omits もの when the meaning is clear.

What exactly does 以外 mean, and what patterns does it appear in?

以外 means “other than; except (for).” Common patterns:

N以外のN: 現金以外の方法 (“methods other than cash”)
N以外は: 現金以外は使わない (“I don’t use anything except cash”)
N以外も: 現金以外も使う (“I also use non-cash methods”)
N以外に: adverbial/locative sense: 現金以外に何がありますか (“Besides cash, what else is there?”)

What does も modify here? How would the meaning change if I moved も?

Scope changes with placement:

彼女は現金以外も使う: She uses non-cash methods too (in addition to cash).
彼女も現金以外を使う: She too uses non-cash (someone else does as well).
彼女は現金も使う: She uses cash too (in addition to non-cash). Choose based on what you want “also/too” to apply to.

How do I say “not only cash but also cards” more explicitly?

Use a “not only … but also …” pattern:

現金だけでなく、カードも使う。
More formal: 現金ばかりでなく、カードも使う。

Is 使う plain? How do I make the sentence polite, and should I mix styles?

Yes, 使う is plain form. Polite version:

私は現金をよく使いますが、彼女は現金以外も使います。 Keep one style per sentence in most situations; mixing is usually avoided except for certain softening effects in conversation.

Does 彼女 mean “she” or “girlfriend”?

Both are possible. In narratives, 彼女 often means “she”; in everyday conversation it can mean “my girlfriend.” Japanese avoids third-person pronouns more than English, so using a name or role (e.g., 妻, 友だち) is often clearer.

What tense/aspect is 使う here? How do I say “used to” or “these days”?

Plain non-past in Japanese often expresses habitual actions. Variations:

Past event: 使った (“used”)
Past habitual: よく使っていた (“used to use often”)
Ongoing: 使っている (“is using”)
Add time adverbs for nuance: 最近は現金をよく使う (“These days I often use cash”)

Are spaces normal in Japanese?

No. Spaces here are learner-friendly. Standard writing is:

私は現金をよく使うが、彼女は現金以外も使う。

Can I replace が with けど/けれども/しかし? Any nuance differences?

Yes:

けど/けれども: conversational (けれども is a bit more formal).
Example: 私は現金をよく使うけど、彼女は現金以外も使う。
しかし: more formal/written, often sentence-initial.
Example: 私は現金をよく使う。 しかし、彼女は現金以外も使う。

Can I say 現金以外にも使う?

Not for this meaning. に with 使う marks a target/purpose (e.g., お金を旅行に使う “spend money on travel”).
現金以外にも使う would require a different direct object, e.g., お金を旅行以外にも使う (“I spend money on things other than travel as well”). In our sentence, we’re using non-cash methods as the direct object, so 現金以外も使う is the right pattern.

Why is は pronounced “wa” and を pronounced “o”? How do I read the whole sentence?

When used as particles, は is read “wa” and を is read “o.”
Reading: “Watashi wa genkin o yoku tsukau ga, kanojo wa genkin igai mo tsukau.”