I don't see it that way, I know everybody else does but I don't think it's that, I think it's more of a brother/sister thing, and that's probably going to have some people scratching their heads thinking 'what the hell?' but that's how it makes sense to me.
It reminds me of something from Homicide: Life on the Street, Kay Howard and Beau Felton were partnered together and you kind of got the feeling there was something between them and in one episode Beau actually said he loved her, but, and even though he didn't say it you can tell it wasn't like that, she was his partner, like Olivia is Elliot's partner; they've known each other for so many years and they are heavily involved in each other's lives at times but I don't see it as being a romantic thing at all. I see it more as Elliot being the overprotective big brother.