But they could have made her a good person just doing her job and actually had her get to the same point that she has without all the shady behavior.
Don't have her date Oliver. Just have her be digging into him as a reporter. If they really needed her to see his Bratva tattoo, have her throw coffee on him or something to get him to remove his shirt. Have her walk into his office while he's changing shirts or something. Have a photo pop up somewhere that shows the tattoo. Etc. The writers could have come up with something.
And really, any reporter should probably be able to put together who's GA, who's on the team, etc. without needing to hire a PI to do the work. GA just so happened to show up in Star City at the beginning of S4 when Oliver Queen returned to town, just like the Hood showed up in S1 when Oliver returned. Then there was Oliver revealing LL was BC and this group of people hung out with no one else but each other, so someone should have put the pieces together. Oliver disappeared at an event earlier in the season and then GA appeared moments later. No one questioned that. The list goes on.
Maybe then Susan wouldn't be so hated. Instead, we have to deal with this "relationship" that makes Oliver look ridiculously stupid and that they're trying to make seem so important that the other relationships in his life are suffering/nonexistent right now.