well, i'm squarely in the "OMD was a terrible idea, bring back MJ, and I don't care at all about Peter and Carlie's relationship" camp, so my opinion probably isn't non-biased.
That being said, the way i read it was that Carlie was pretty staggeringly drunk and clearly not thinking straight. I'm pretty sure she won't remember it the next day, and she definitely will regret it. (Again, assuming she actually gets the tattoo. They don't show it happening).
On top of that, I'm not sure that everyone knows everything that Norman did as the Green Goblin. It's public knowledge that he was the Goblin, but not until recently when he was arrested for the first time in the first few issues of The Pulse (well, second - but the first time he was released by the Scriers and they killed anyone who had seen that Norman was under the mask). Before that everything was covered up. Plus there have been several Green Goblins (as well has Hob Goblins, Grey Goblins, DemoGoblins, Protogoblins, and so on) so I'm sure the general public in the Marvel universe doesn't know everything that he's done. I don't remember reading that Carlie knew Gwen (but I could be wrong about that) and I'm pretty sure Peter and Carlie haven't talked about Gwen on-panel, maybe they have off-panel, but who knows. And she probably wouldn't know about it without him telling her. Gwen's death was a big deal to the readers, but if you lived in a city full of superheroes that was attacked by Skrulls, Galactus, Ultron, Kang, Magneto, etc every other weekend you probably wouldn't remember a girl that was thrown off a bridge by a villain several years ago, and you certainly wouldn't know who her boyfriend was at the time.
That said, she did say that she was doing it b/c she knew Peter hated Norman Osborn. And she does know Harry, but (if I remember correctly) only through Peter and Lilly Hollister (both of whom she regards as terrible people at this point).
So, in my opinion, it didn't come off as completely horrible, but it did come off as not being important or very worrisome. And that's saying something considering that as far as I'm concerned, the relationship stuff between Peter and Gwen/MJ was the heart of the book during 70s and 80s, as well as a lot of JMS' run.