Dilemma♥

OK so something has been heavy on my mind for awhile now, so what better way to deal with it than to seek advice from people who actually care about my randomness??
So I had (yes, had) this friend. She was a best friend, actually… we’ll call her B. She’s 2 years younger than me, but she has a baby and is married. Her husband (that’s so weird to say since they’re so young) is on my boyfriend’s wrestling team, and they were roommates their freshman year. So B and I became close, we’ve even made a road trip out to Iowa together to surprise the boys for Valentine’s Day, used to talk and text all day everyday, and I’ve been to her home (when she lived in her hometown, in Indiana) and all that… so yeah, we were close.
So this past summer, my boyfriend was here to spend the week of my 21st birthday with me, and during that week, B calls me and tells me she has a question but she wants to ask me when my boyfriend isn’t around. Ok…weirdness, but whatever. So some time later that week, I was out driving from work (alone) and she called and asked her question. B wanted to know if my boyfriend has ever smoked weed with her husband.

*record scratch*

Backtrack: B’s husband supposedly never drinks, smokes, or does any freakin wrong in the world. My boyfriend smokes weed. It bugs me, but that’s a whole ‘nother blog post. Anyway, a few months before B asked me this, my boyfriend had indeed told me that after a big argument between B and her husband, husband needed to get out of the house and cool off, and ended up partaking (for the first time) in the recreational activities, if you know what I mean… but boyfriend asked me to swear not to tell B, because we all knew she'd flip out. So I swore.

*back to July*

So when B asks me this, I play it off… I say “I don’t know, have you asked -boyfriend- about it?” and B says. “No, but hey I gotta go. I’ll ttyl”… we get off the phone.
I haven’t spoken to her since.
I found out later that B's husband came clean and told her about what he'd done. I mean he had to. I'd never mentioned it to anyone, my boyfriend wouldn't, and no one else in the world knew.
Now since we’re all grown here, I’ll admit that once I realized I’d been kicked to the curb, my feelings were seriously hurt. I don’t have too many real friends, so the ones I do have mean a lot to me. B was one of them. My feelings are still kinda hurt, but what I want to know is, am I wrong for not telling her the truth? Who does my loyalty belong to? My man, even though he was in the wrong for corrupting B’s husband, or B since we were supposed to be best friends? I was stuck between a rock and a hard place, and I didn’t even put myself there! I was upset because I never asked about what B’s husband and my boyfriend did that day. Boyfriend volunteered this information to me. The upsetting part was that I lost a friend and I felt guilty because yes, I had lied to her…but I was also upset that I’d been forced into that situation. (Boyfriend has been cussed out thoroughly reprimanded about this matter, many times since)
Even now, boyfriend has told me that B’s husband has smoked with him more than once (which I’m just learning) and last night they were all drinking with other members of the team after a tournament. So that’s another blow to me, because apparently B has no problem with my boyfriend still hanging out with her husband, in their house and everything…yet she can’t even speak to me long enough to tell me that she isn’t speaking to me anymore. Her husband is still doing his thing, (although I'm not sure if B knows or not), and she's fine with it. My boyfriend still hangs out at the apartment with B and her husband. She's fine with it. I'm the only one left out in the cold, and I wasn't even an eyewitness or a willing accomplice to the situation. Thoughts?
x0x0♥