Me [30, F] with my friend [30, F]; I want to fuck her long time crush [35, M]

Throwaway.

I’m lonely, I broke it off with my boyfriend of 4 years 5 months ago and I have not even exchanged a sexy glance with someone in all this time.

I went to a concert at a small basement place last night and ran into a guy (let’s call him “B”) I haven’t seen in ages. My best friend, whom I’ve known since we were 6 and who is a sister to me, spent over 6 years of her life being madly in love with him a very, very long time ago. He never reciprocated; they kissed once and he apologized saying he saw her as a friend. My friend and I have always been opposites in social circles, looks, music taste; I used to run into him quite a lot while going to concerts or bars at night back then, but I sort of hated him because I felt he made my friend hurt so we didn’t really speak. Then he moved away to Germany and we never saw him again.

Now, more than half a decade later, I run into him at this concert. He’s back. He’s sexy as fucking hell, I see it now. He approached and we talked about our lives and deep in my guts I felt there was chemistry. According to my friends who were there he stared at me all night and tried to approach me whenever he could. I left early anyway.

As for my friend, she has been in a relationship with her awesome boyfriend for the last 5 years. Her bf is an amazing guy: caring, treats her like the queen she is and the guy is completely in love with her. They’ve just moved in together; they have a beautiful home and are starting to talk about having children.

The issue is that she told me she still dreams of B sometimes. She has also told me that she loves her bf but sometimes is scared that she never really felt again the crazy passion she felt for B for anyone else, though she was sure she loves her bf and wants to be with him.

B has reappeared now, she doesn’t know it, and it turns out that in this period of loneliness were fucking options are not really raining on me I meet him and feel like I want to fuck him badly (and think he’d want so too). I’m usually quite upfront with guys and I would be a lot more... proactive if I didn’t have this massive doubt: will I be a shitty friend if I intend to hook up with him?

I’m afraid it would hurt her -maybe even put our friendship at risk- if I pursued something with this guy. But I really want to play the “we’re adults and you’re almost engaged and planning family with your great bf and I’m single and horny and you haven’t seen or talked to this guy in like 7 years” card. Would it be awful of me to do something about this guy? What would you do?

tl;dr: Am I wrong to pursue a very old long time crush from my friend who's been in a great relationship for the last 5 years?