From the way she sees it, Five is always the one trying to carry all of the family burdens and he's willing to do it all by himself. Whether that's because he's just gotten used to working alone, doesn't want his family to end up dead (again), or because he's a little shit that just thinks he can do it all on his own - in this case, it's just because Lila has knowledge of future events and knowing who she'd rather know this secret.

Lila is putting this fact in Five's hands over someone who knows what it's like to be a parent, a mother. That should bring up so many questions in anyone's mind. Of course, if Diego was still here, he'd be the one she was telling instead of Five, but here they are.

If there's one thing she's learned about this family, it's that they're more hurt by all the little lies and secrets over the physical violence done to them. Lila had been ready to go through all of the Hargreeves to get to Five on that farm, but they'd hardly blinked when she rejoined them in the new timeline.

"Fine. I'll let you know if I get picked for a special assignment." No hesitation to agree to more than just accepting errands from the Merchant. She doesn't know if anyone else would give her secret tasks, but might as well include them too if they're going to make this deal. Having as much information as possible before stepping into trouble would only benefit her. "Just don't expect me to sit out everything because it's dangerous."

She might be pregnant, but Lila is also a trained assassin and would only rebel harder if Five (or anyone) decides to treat her like a fragile piece of glass. If he can respect that, then she can accept when he tells her to stay out of certain things.