Here's my problem with the whole "tell her bit by bit," "only give her so much information," "don't tell her anything until...?" approach: I believe it puts the person from whom you're withholding the information into a non-consensual position.
She didn't decide to be with a person who couldn't simply be happy with her. She needs to know what is going on so that she can make informed decisions about her own life. I understand that these kinds of things often develop over time, and that one doesn't always know in uncertain terms what is going on, but honestly the FIRST time you had feelings for another person you really should have talked to her.
What is going on, until some sunlight disinfects the situation, is a power-play. You want to control the flow of information in the relationship so that you may experience the best outcome. Your partner right now doesn't have an opportunity to look at the facts for herself, and decide *for herself* what is best for her.
I'm not trying to shine a bad light on you- you sound truly perplexed yourself. I wish I had known a lot sooner what the whole truth of my situation was- I don't know that I would have made any different decisions, but the opportunity to do that would have been there. Now, I have built a history with a woman I love dearly, and I am *put* into a tight spot I didn't decide to be in. I don't think my partner was tricking me or trying to deceive- she just left out information that she thought I would find unpleasant.
Now, in my case, I am not leaving because I see that my partner has been sacrificing expressing her desires in her own way and she has done that so that I would not be hurt. I feel like I have to at least try and face some of my own fears before I can say I want to go it alone. I don't know how it will turn out. I have been thinking all night.
I'm sorry if this is untimely and you have already resolved your issue, I have just been chewing on the best way to word my thoughts. You will have to put some trust into your partner and let her have the space to make her own decisions eventually. It is in better faith to be up-front than it is to try and "groom" her to accept what it is that you want, or to drop hints. One of these days, it is very likely that you will have lamented and thrashed about and you will act on one of these love interests- and she will not only be within her rights to terminate the relationship at that point, she will have a very valid reason to never trust you again.
If you are honest, and you speak to her before anything else happens, she might have more trust in you than you ever imagined. (Then again she might not. But in this case, it's my opinion that you are the one who has the burden of taking a "leap of faith.")