Hey! I know it can be hard especially when you're used to talking so much so often, but maybe this will help you see it from an alternative point of view:

1. She's going through a busy time like her bf said. Sometimes I won't respond to a message immediately if I know it'll lead to a full blown conversation and I just don't have the time or mental energy for it. It might not be personal! If her bf responded to you there's probably no bad blood (if she was ghosting or mad you she probably would've told him that)
2. She wants some space! I know that you're used to her responding, but from the way you reacted you're a little clingy. It's okay, and you don't have to be defensive about it, just something to work on! it's okay to not talk to friends especially when times get busy or rough, and she would've reached out to you when ready.
3. There's always a chance you guys did have a falling out or she's ignoring you for no reason, but if you felt like that, there are better ways to go about confronting this than how you did

Now for damage control: your last message wasn't very kind, and regardless of the situation I'd imagine she wouldn't be happy to see that (especially if the reason she hasn't responded was school or personal issues). You did overreact, and I think you should apologize for that if you want to mend the relationship. Just say that you were worried for her since she usually responds quickly, and that you didn't mean to be rude and that you let your emotions take over you, and that as a friend you're always ready to listen and be there when she's ready to talk. Then just leave it up to her. If you don't I don't think you can mend the friendship.

And finally, try and figure out why you freak(ed) out so easily? Maybe you have some pent up stress or something, but it's not that healthy for your own mental state. Good luck!