Friendship Advice

Sorry this is very long.
So my best friend (I'll refer to her as B) is very mad at me and I don't know what to do. I'll try my best to make this clear.
On Friday, my school takes us to this sport centre for PE and we get dismissed from there. I usually go to buy cake and then go home with my other friend (who I'll refer to as C). B usually goes home with her friend, but she wasn't in so she tagged along with us and we asked if she wanted to get cake with us which she said yes to.
I'll try to make this part clear because it might be confusing, but there are two ways to the bus stop near where we buy cake- one is straight ahead and the other is through this alleyway. So B started saying she knew the way and so we told her okay then continue (she was going on the straight path). As a (bad) joke, C and I decided to run through the alleyway as the two paths meet and we'd thought it'd be funny if we were actually in front of her.
Anyways, we see B and wave but she goes on her phone and pretends not to see us. She turns around and crosses the road and leaves and C and I are confused but we buy the cake and head home.
I texted B, asking why she didn't come and get cake with us. Four hours later, she replied saying we told her to "F off" and that we were making fun of her but she "gets it" because C and I have been friends longer. I replied apologising for the joke and that I get it was hurtful, but I told her we never made fun of her. She replied saying she was not going to reply to what I just said because it was very hurtful and that she was upset, so I apologised again and I told her I understand our joke was very distasteful. She then left me on read and wouldn't speak to me at all.
Today, we were playing card games and she asked for cards so C and I ignored her because she wasn't talking to us and we were annoyed. She then turned to her friends and started calling us things in another language. I also learnt she was telling one of my big secrets to my friends, which really angered me because I told them to her because I trusted her.
Sorry if this was long, but I don't know what to do. I'm confused if I should talk to her or not, she is my best friend, but I don't know if I still want to be friends with her or not.

Hey! I hope you’re ok, I think I understand where B was coming from. Even if she normally doesn’t feel like this, she might have felt that you and C are the closer ‘duo in the trio’ iykwim, when she asked to get cake with you guys she probably already felt like a bit of an outsider by intruding on your routine. It’s likely she felt that point of tension the whole time, so the small joke of you guys running of without her could have felt like a bigger deal. I understand why she’s upset, even though you didn’t mean it might have felt to her like you were signalling you didn’t really want her to be there. I would apologise and explain that you did really want her to come, maybe make a gesture like asking all of you to go out for cake this week. But it’s totally unfair she was telling you secrets and excluding you by speaking another language, the latter maybe don’t bring up as she might view it as you being upset when she leaves you out of cultural things - that didn’t make sense but trust me from experience. Btw getting cake every week is such a fun thing to do I’m jealous!

Heyy, tysm for the response. The thing, is she does act like this a lot, I get that it's coming from insecurities since I believe she got left by some people in the past. I understood she was upset and I felt very bad about it, so I told her I get it was a very bad thing of me to do and I apologised, however I'm just confused why she's not talking to me now. I would invite her to get cake next time but whenever I even sit with her she'll turn away and not even look at me. I'm really scared though since we've been friends for like a year BUT that secret she told is very bad, like I'd lose my friends over it so I don't know why she thought it was ok to say. Ty for your response and guidance!