[X] Tone: steady, firm. Look Kyouko in the eyes. You came out here to help her because you wanted to since she deserved it, not to win her favor or somesuch. Steady, soft: her owing you is something you don't want. You want Kyouko to do things for Kyouko, not for Sabrina, because Kyouko really needs that.
-[X] In response to an assertion that Kyouko doesn't deserve something: apologize for being worried about being overheard, warn Mami via telepathy, privacy sphere from enchanted grief. Include Yuma. Drop the metabomb: minimize details, note that you've been telling your other close friends about it, you know a lot of peoples' rough backgrounds, though not your own. Assert that you know all about the events that lead to the Sakura church being abandoned, and reaffirm that Kyouko deserves good things. Do not talk about specifics of Kyouko's past unless you are challenged to.
--[X] Otherwise, cut to voting quickly.
[X] Absolve Kyouko of debt as much as possible.
-[X] Kyouko deserves this. Everyone deserves a place to call their own.
--[X] You just did the right thing.
-[X] Acknowledge how important this is to her; contrast with how little effort it took you and Mika.
--[X] For how much this costed you, you'd accept her heartful thanks. Wouldn't say no to a hug.
[X] Metabomb.
-[X] Afterwards, ask something of Kyouko and Yuma, as friends.
-[X] Privacy device. Normal warnings, and watch out for those antennas.
-[X] Remind them of your weird knowledge; reveal your hipotheses about your nature. Don't jump right into you knowing their past, but build towards it.