"Ambivalent" would mean you simultaneously love and loathe her. Sounds like you're more indifferent. sorry I can't help myself it's an English major thing that's a really useful word that's been made useless by conflation with a totally opposite concept sorry
'S funny, though, that what you've just described is a big part of what, as a Donna convert, annoys me most about her treatment - because that's such a completely natural post-Crisis Diana fan attitude to hold. I felt pretty much exactly the same way until fairly recently, and who wouldn't? She's got nothing to do with Diana, all of their interaction feels really forced and false, she never does anything interesting or useful in Diana's world and the one time when she's actually around regularly in a well-integrated way (Jimenez) she's annoying as all getout and completely fails to accomplish anything meaningful or important even when she's theoretically significant to the plot. She adds nothing and subtracts much.
But she shouldn't be that way, and she doesn't have to be. She's a meaningful and interesting character in her own right through her Titans years and in DARKSTARS, and she does add something valuable to Diana when their relationship is done right - when they're actually sisters who love, trust and know each other like only sisters can, as opposed to random strangers with a vague and meaningless "connection" (or as opposed to pretty much any of Diana's other long-term, strong relationships, which are always either maternal, or with men - usually romanticized and never truly emotionally intimate). The fact that that never quite gelled in the entirety of volume 2 is shameful.