Oh, Stage Star!
I'm sending you lots of *hugs*, even though I dislike touching people/having people touch me. That's so rough! I mean, because you haven't committed the "bad thing" you aren't hurting?
People need to understand that all emotions and feelings are legitimate, even if they are not correct. If I feel badly because you said something to me, that's legit. Even if I feel badly because you said something and I misunderstood it (so your words weren't offensive, I just didn't hear it right or something), it's still alright for me to feel bad. BUT! And this is a huge BUT! Your feelings still matter, they are still real, and you're still hurting, so for your friend to be so harsh to you was uncalled for in a big way. No one should judge whether or not you're hurting more or less than someone else.
I think that a "real" best friend would have tried to make you feel better rather than belittling your emotions. At this point, and from what you've said, I think you did the right thing in making her your ex-best friend. Real friends don't say these sort of things. However, if you (and she) take some time, come back, and discover that she didn't really mean what she said, then maybe try to make up. This isn't a have-to, just a suggestion. She might have been really angry that day about something else and let it spill over onto you. Or she may just be a jerk. You have the right to decide who you want your friends to be, and people that minimize or mock your feelings can be kicked off the list without a second thought.
I just wanted to mention that she seems to think that depression isn't a big deal unless it results in, well, death. Accusing you of being a bad friend on a day that was difficult for you--in my book, she crossed the line.
Basically (if you've gotten this far, give yourself a cookie!), I think you made the right choice to drop her. In a few days, if (and only if) you want to reevaluate, go ahead and do that. She doesn't seem sympathetic, and you need a best friend that you can talk to about these things. It's one thing to "understand" (empathize because you've been there) and another thing to be "understanding" (sympathize because you see how it's hard for someone else to be dealing with it). It doesn't seem like this girl/woman can do either.
There are others, especially here, who will do both (sympathize and empathize) intensely. I know that internet friends aren't the same as physically there friends, but until you find a decent one, maybe just rely on people who won't be unkind to you when you've made it clear that you're having a bad day.
Lots of hugs again to you, Star. It's tough when "good" friends don't understand, and worse, get snippy and mean. Just know that we're here for you!
cutebutpsycho

<--I mean that to be a hug, not a creepy, grabby move.