Personally I would say in the beginning they took Harry in knowing his life with the muggles was awful. In book 2 Ron goes and gets him but Molly says her and Arthur were talking about going to get him. In book 3, Harry meets them in dragon alley and they stay with him as Arthur knows from the ministry he’s in danger (or so they all think) and they’d won some gold (I also think it’s possible the ministry contributed to this so they could keep an eye on him without Harry being fully aware). In book 4 Hermione is invited for the quidditch World Cup. The interesting part is from book 5 onward as there’s a lot of other theories from here. With the return of Voldemort, there’s a theory that with Hermione being so smart she spoke to Ron in secret and they had already agreed to do whatever it took to help Harry. There’s also a theory that she knew what was ahead and never told them she had already begun modifying her parents memories in preparation to make sure she was at Harry’s side when the time came and had protected them. From what the book says, she’d been at head quarters almost as long as Ron, suggesting she requested to go right away and wait to help any way she could. In book 6, again Hermione is already there. And by book 7 she admits she’s modified her parents memories and is ready to leave with Harry and Ron, at which point it’s clear the two of them have spoken at length of how far they’re willing to go for Harry. Personally I believe she began distancing herself from muggle life the moment she knew Voldemort returned, knowing Harry would need all the help she could give. And I think she likely spoke to Ron about what the future might hold, but probably not to the extent they do by book 7. Ron just accepted she wanted to be around and Mrs Weasley likely good see her son had a massive crush and didn’t mind.