This isn't much of a spoiler, but it is about Kelly and romance. You can romance Kelly and another crew member. Really it's more of a fling with her and the other crew members won't even say anything about it. The advantage is if you do invite her up to your room and then go for the one-night stand, she'll offer to feed your fish for you. By the way, if you bought any fish on Citadel they'll die if you don't feed them regularly after missions Romancing Kelly means your fish will still be alive for ME3, while I think they may die between games if you don't.