It wasn't just her wanting to stay under the radar. If she did this for him, it'd mean having to see him every day. Having to be reminded of how she could have stopped it.
Not that she feels guilty.
She tries to forget it after she leaves, but knowing that he's found more on her brother in a few days than she's managed to come up with in the past nine years bothers her, and guilt or something similar is weighing heavy on her mind. She hadn't even bothered to say no, just thrown the file back at him and walked out. Looking back, maybe that was a little harsh, but she had been pissed.
She sits for hours, going over possibilities in her head. It's not like she owes him anything. She never asked him to do this for her.
But he did it anyway, when he could have just dropped the whole thing when she made it clear the first time she wasn't interested in helping him. Even more than the information on Zack, she can't ignore that. Can't walk away from that, no matter how much she may want to.
So she finds herself at his apartment the next night, picking the lock and walking in (noticing it already feels comfortable to do so). She finds him by the picture window (he's had it fixed by now) with a glass of wine and he turns when he sees her in the reflection, looking somewhat but not entirely surprised.
She almost smiles at him, but doesn't. Instead she looks at him with a blank expression, her everyday mask, the one she's used to wearing but already feels like she can drop around him.
"So what is it you want me to do?"