Technically, 6O owes A2 nothing at all - especially not with her saying such distressing things and hacking her way in! But without A2, 2B wouldn't exist at all, and 6O doesn't want to see anyone else die. Or malfunction. She can't bring back A2's lost companions or undo the past. She can't make Command change the past or their policies either. But she can still fulfill at least some of he functions here.

It doesn't matter if humans are alive or not back home. There are humans here. And there are androids here. And the android right in front of her with the face so similar to 2B's looks like she could do with a tune up.

Maybe. But are you actually doing it? And why did you take off your clothing?