I think I'd ship Ivy and Rachel if Ivy didn't scare Rachel so much. Rachel clearly has so many issues with not wanting to be a vampire or vamp servant, that I (and this is just me) can't get past that to ship them. If Ivy were still the same personality but was, like, an assassin instead of a vampire, I'd probably ship them too.
Re: SPOILERS FOR THE MOST RECENT RACHEL MORGAN BOOK!