I like my best friend, but so does she... Options

[soramimicake]

Okay, this may be kind of long, so bear with me...

My best friend is a guy who, obviously, I spend a lot of time with. We're in the same major, so we study together and hang out a lot. We have a really intimate relationship in that we each tend to be the main confidante of the other in pretty much all situations. For the past...while...I've started developing serious feelings for him, but the situation is kind of complicated, so I'm not sure whether or not I should pursue a relationship with him. I know that he's liked me for awhile, but I was in another relationship for about a year of our friendship. We've recently been flirting more intensely than normal, and he asked me if I was fully over my ex-boyfriend (I said that I was).

So, here's the problem. About a year and a half ago, one of my pretty good friends had a super crush on him, even though she'd only known him for a few weeks. She definitely hasn't let this go, and is now in a state of constant anger with him even though they were never together and he turned her down politely. She often comes to talk to me to confide about how she's still interested in him but hates him at the same time. There were also several instances a couple of months ago when she came to me extremely angry at the fact that he and I spend a lot of time together. She said that if she didn't know any better, she'd say that we were dating and began to tell me how angry this would make her, and how he was being cruel if he was pursuing someone who was one of her friends. I told her that he had a right to date anyone he wanted, especially since they had never dated, and she took this as me saying that we were going to date, which, at that point, I thought seemed unlikely. Now that there's a possibility of a relationship happening between he and I, I'm not sure what I should do. I thought about talking with him about it (he's who I'd usually talk to about stuff like this even though it's kind of weird), but I also want him to make a move or assert that he'd like us to date before I bring up the topic. However, at the same time, I almost feel like that would be deceitful towards her. But, also, if I tell her that I like him, she'll be extremely upset and everybody will know pretty much immediately.

Okay sorry that was long...does anyone have any advice on what I should do?? Thanks!