I'm Dr. Jackie, an interpersonal communication researcher/professor and relationship expert. And I want to help you with your question. First, I am very sorry that you are very likely conflicted and in turmoil.
Second, I'd like to ask a few questions of you to help me understand the entire picture better. Did Claire first begin to date you and/or does she live with you for the most part? Also, does she know that you love her as more than a friend but as a lover and girlfriend? Can I safely assume that Stacey is the friend with whom she is in love?
I always believe (and research supports this) that being open and honest and up front are much better than doing the opposite, especially for the long run. In this situation, if Claire does not know you have romantic feelings for her, then she may be hiding possible romantic feelings for you. People do this to hide their vulnerability--as soon as another person knows we are interested in them, we make ourselves fragile and open to rejection.
If you HAVE made your true feelings known to her, then you do know that she must think a lot of you because she flat out told you that she loves you. Of course, I know you want her to be IN LOVE with you. And if you do feel that she is attracted to you romantically, then showing her you truly care about her and want what is best for her is the absolute best way to keep those doors open. It could be that Claire is romantically interested in Stacey but maybe she does not have the friendship bond that you have with her. And if that is the case, then again, you have a better chance in the long run to win over Claire and show her that you can be a best friend and lover both to her.
Please do understand that I am not suggesting that you "sit around and wait." In fact, Claire seeing you going out, maybe even dating some girls just to go out and have a nice time, might be appealing to her. If you cut yourself off and just sit at home and wait, Claire is less likely to see you as attractive just because most people are attracted to people who enjoy life, like to go out and have a good time, etc.
I hope this is a good start. If you can comment and give me feedback to what I have stated and asked, I think I probably can provide you an even better answer and recommendation. And I can't see the screen right now that shows if you requested a phone/Skype consult. But just in case you have, I'll send you my contact information so that you will have it if you need it.
Please take good care! I look forward to hearing back and working with you,