Yeah, she really didn't miss the tone in her voice. Buffy would have to be a moron to see that some part of Ruby was jealous. Maybe not of the fact that Sam had a girlfriend- because wasn't Ruby with the Angel? - but maybe of the connection, or closeness.
"I honestly don't know what to tell you, Ruby." she said, frowning. "I don't think there is a way to...make this go away, of fix it. All I can think of is eventually proving that you are who you say you are, and that's going to take time." She still didn't know Sam, or anything about how he worked. For all she knew he was totally set in his frame of mind, unable to change.
Then her mind flipped back to Rubys last question. Well, the demon was being honest with her- or at least Buffy thought she was being honest with her, so maybe she deserved honesty in return. "Yeah...I guess I do feel replaced." she said glumly, referring back to the question. "Angry, I guess. It worked twelve years to get to where I was, only to have it taken away because the Powers want a Buffy Summers from a specific time line in the city. Now I have nothing. Maybe if I'd done something to deserve it, it would be different. But." she shrugged. "I really don't think I have." Maybe she was more pissed that Faith had done some good in..what...a year? And landed on top. She'd been giving it all for twelve years and had nothing. "I guess being dethroned by your perfect rival without even knowing or being here to stop it sucks. If that makes me petty, then I'm petty."