I wouldn't say 'numerous times' she helped once by deliberately using a shoddy paralysis spell, and once by holding the hedge open for him- neither of which can be reasonably traced to her.
And in WN she was involved because she was a potential target.
No, she was involved because she was
hired to be, and it went from there. Remember, she's taken a leaf from Harry's book in advertising her magical services.
As for her being on the Grey Council, it's possible, but I doubt it. For one thing, she's made a long habit of avoiding the notice of and involvement with the White Council. The Grey Council is, at the end of the day, an extension of the White Council. It might be that not everyone in the Grey Council are official members of the White Council, but I'd bet the majority are, and she'd be hanging out very close to people who are at the heart of the Council.
Which is not to say she doesn't know some people on it (besides Harry) or hhasn't worked with them at some point.
Rather than evil, I'd classify her as selfish/cowardly. She's willing to help, but only until she herself comes under fire- at which point she starts looking for people to throw under a bus in her place.
That's too harsh, based on what we've seen. The first betrayal of Harry was, apparently, the result of mind control, and she ran to Summer and made deals there. Harry was captured by the Wardens and ended up with Ebenezar. In that respect, Harry was luckier, though it probably didn't look that way at the time. Events could have gone differently.
Elaine betrayed Harry to Aurora...but then betrayed Aurora to Harry, and that's
risky. She kept faith throughout
White Night, when it would have been easy to run, too.
It could be, of course, that everything we've seen is an act or a cover, and behind the scenes Elaine is the Big Bad or working for them knowingly. But there's no evidence for that.
My 'take' on Elaine is that she's borderline. She's scared to death, psychically scarred by Justin, and trying hard to decide who she and what she wants to be. Also, and I think this would shock Harry to his core...I think she's trying to live up to Harry's moral example. She's seen what he made of his life after Justin's betrayal, and I think she's impressed on some level. She does seem to be patterning herself after him in some ways.
Harry thinks of himself as a shady kind of guy, trying to do his best but deeply distrusting himself. On some level, he tries to live up to Michael Carpenter's expectations, I think. It's probably just as well, for him, that he doesn't realize that several people he knows consider
him someone setting a standard they try to live up to.
If the Formor approached her with a deal like "give us some names from these places and we'll leave you're town alone" I can see her taking it.
So can I. I can also see her frying the Fomor to a crisp it its own grease, too. She's that close to the borderline and could end up going either way.