In terms of how I'm interpreting the sentence, "livid devilish kisses" is serving as an appositive for "nasty scars". To me. "the marks of injection" seems more of an explanation of what these scars are, so, because it's an explanation, you would actually use a colon.
There are nasty scars, livid devilish kisses on her snowy innocent arms: the marks of injection.
Note, though, that this places importance on them being "the marks of injection", and I'm not sure if this is what you intended.
In terms of using "marks of injection" as a simple appositive, which would require a comma, it is separated from what it's modifying, the "nasty scars" and/or the "livid devilish kisses", by "her snowy innocent arms". Grammatically, this would lead the reader to believe it refers to her arms, so in order to use it like this the sentence should be reordered. It is obvious this is not what it refers to, but modifiers and appositives should be next to what they modify, so in this manner it is confusing. You could try using:
There are nasty scars, livid devilish kisses, the marks of injections on her snowy innocent arms.
A dash would work in both of these uses, though dashes bring more emphasis.