[X] She's already started doing it. The guardedness and barriers she's built up are like the social equivalent of having a limp because she broke your ankle saving someone. With just the changed context of knowing what she fights for, instead of making her seem untrustworthy, they show how she's fought and suffered for a long time, trying to do the right thing. Just from reaching out, it's let everyone see her more clearly.
-[x] She's been trying to keep Madoka away, scare her away, for a long time, and you can understand why - but without the context, that made everyone interpret Homura's actions in a really bad light, and it made *Homura* see everyone in a bad light too - she always saw their suspicious side, instead of how caring they can be to their friends. Here and now, relaxing where she can, giving herself permission to laugh, smile, and joke when she can and just *interacting* with people, will see Madoka and Sayaka continue to get closer to her, and see her learning more about them in turn. It's emotional, social recovery, in the same way that physical recovery requires a sort of gentle exercise rebuilding.
[X] But... Homura probably isn't just worried about here and now, is she? You've been avoiding bringing it up, since you know it'll hurt, but... you don't want Homura to feel totally reliant on you with what has to feel like a brittle sort of hope. That's not fair to her.
-[x] You know that Homura likes to be able to reason her way through a problem. So here's your advice, that won't ever be needed, but should still help Homura settle some of the doubts she must feel - if things do go wrong, and she needs to start again. Borrow a notebook and write this down as you talk.
--[x] She has the info needed to actually argue her stance and mission to others, and explain the Incubator's lies. She's seen more of Mami and Sayaka now - and Mami can give her advice on how to convince her past self, in fact *everyone* will be mostly happy to explain their own reasoning to her if she asks them. And most of all... she should make sure Madoka has a place, and make sure she has the chance to see how much her contracting would hurt Homura.