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


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?




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 ~'.

