Why is 何が used to mean “sorry for what?” instead of 何で?

Question

I was watching an anime where character A apologizes to character B after trying to kiss her:

A: ごめん！I’m sorry!

B: 何が？言ってみて！For what? Just try to say it!

My question is why was が used after 何 instead of で, when usually the て-form precedes apology words like すみません and ごめんなさい? You would usually say 〜してごめん！and not 〜がごめん when apologizing, am I correct? So why didn’t B say 何で instead of 何が?

Answer 1

Without the source material I'm half guessing the full scenario.

The が implies an omitted adjective, in this case 悪い. So she's not responding to his ごめん, but to some other, unspoken issue.

何が悪い? What is wrong?

She knows what the problem is, though, so she says 'go on, say it!' (Say what they both already know, that he shouldn't have tried to kiss her, or that he already has a girlfriend or whatever else.)

So, given that situation, if she said 何で (why?), it could imply that she might not know what was wrong. Although she could have said 何で and it would still make sense, the 何が is a lot more direct.

Edit: By the way, you are right that ごめん can be preceded by the て form to mean 'sorry for ~'.

Answer 2

Also without knowing the scene from anime, I try to analyze way of using 何が.

In such situation, B can say 「何で？」 to ask reason why A apologizes. But B chose 「何が？」.　It means B is not asking about reason.

Particle が indicates 何 as subject for something or some action. Something or some action as predicate didn't told at all so that we, including A, have to imagine it.

何が悪い？ or 何がいけない？ could be one of answers but more literally, we would take A's words as it is, at first.

• 何が「ごめん」なんだ？
• 何が「ごめん」なの？
• 何が「ごめん」なんですか？

あなたはさっきからペコペコあやまってばかりいるけど、何が「ごめんなさい」なんだね？

This example is rather idiomatic use for 「何がごめんなさい？」, because 何 is object for displaying apology therefore particle が doesn't support 何 as subject. This phenomenon can be interpreted as similar way of using は instead of を.

• そこでタバコを吸わないように。⇒ そこでタバコは吸わないように。

I would like to draw your attention to a grammar matter that structure of 何がＸＸだ is often used for rhetorical question, such as;

• こんな大戦争を始めておきながら、何が世界平和のためだ！
• 何がお前の将来のためだって？人をさんざんにこき使っておきながら・・・

As a conclusion, from B's speech of 「何が？言ってみて！」, I strongly feel that B is not asking something to A but is trying to teach how A's attitude should be about the matter they have just experienced.

So, 何が？ said by B is under intention of protest to A. That is my opinion.