Elektra/Karen, things you didn't say at all
Elektra never feels guilt. It's not in her nature. She didn't feel it the first time she killed a man, and she hasn't felt bad about any death she's caused since.
So why does she want to apologize to Matthew's pretty blonde girlfriend? It was obvious they weren't fucking; Stick's presence alone should have clued her in, if she missed that Elektra herself was half-dead. The girl is too stupid to survive in Matthew's world if she couldn't figure that out.
She taps her fingernail against her glass. Perhaps Matthew's morals are finally rubbing off on her, she thinks with distaste. Perhaps this is a sign she needs to take a step back, that she's too close to this, to Matthew.
No, that's not it. Elektra knows that's not it. She's … curious, that's all. Curious about this slip of a girl who has so captured Matthew's interest. Curious about what it takes to turn a man's head away from her. Curious if the girl's lips taste sweet, if she kisses soft or bites back, if she'll show Elektra that spine of steel and draw blood with her kitten teeth.
She finishes her mezcal in a single swallow. It doesn't matter now. What's done is done, and she'll be leaving Matthew's city soon enough. If she prays to a god she doesn't believe in to keep the soft blonde alive, well, there's no one here to know.