Well, Vicki is an addict while it seems that Jeremy just uses drugs recreationally, so of course she wasn’t going to want to stop doing them. I think that’s actually partially why she went towards Damon at the end. Probably thought he was tweaking on something and genuinely needed help.
POS = piece of shit
Also, what you’ll notice about TVD-lore is that it frequently deviates from what we think we know about vamps. Garlic is genuinely not a problem for vampires in this universe!