Ha! Two and a half years seems like an eternity? My partner, Kevin, and I have been together for almost fourteen years now. We must be gods!
Were I in your shoes, first thing: I'd count my lucky stars! If Elika already has a girlfriend plus a boyfriend, there's hardly any reason for you to feel squirmy about your indicating that you, also, might like to have another lover (at least). [Know, here, that when I say "lover" I don't mean it in the half-assed cheesy way many people use the term -- which emphasizes sex *way* more than the love part of the word.]
So my advice is to just come right on out with the fact that you are just like her -- interested in a way-of-life that includes or may be welcoming to multiple loves. This part should be easy, and you should waste no time about it. After all, you've miraculously won the tripple gold without even trying: Your partner loves you, is poly, and you love her. What in the heck could be wrong with that?
Then wait a half a day, a half a week or a half a month and say ... "by the way, honey, I think your gf is pretty darn ... neat/fantastic/sexy/hot ... choose words with care.
This should be as easy as falling off an peeled and oiled log, my friend. You have no idea how lucky you are compared to some of the poor, poor folks who've been pouring their wounded hearts out in these fora.
PS -- Was unable to figure out how to make the user-name switch, and have posted a message about the issue in the Moderator's Forum -- which you don't see ... cause you're not a Moderator.