Don't blame him - you only know her side of it. And if you come down on him and they get back together, you will be, in her mind, a problem. Right now she is calling you for advice, and that is awesome! So many moms of teens are truly envious that she's not rejecting you but inviting you in! So nurture that!
I'd let her vent her feelings, don't try to give her answers right away, but help her sort out things. What did he really say, what did he not say, where (if anywhere) did she take it too far and ascribe meanings that were not intended, how much is based on her other feelings of embarrassment or rejection by others (e.g. was there a public aspect to this because of a rumor), what is the role of bullying and rumor in a high school, etc. etc. Then, she needs to learn how to deal with difficult people - this is a relationship skill, a job skill, a getting-along-in-college skill, and so on. In the same way that you gently probe to find out what she's thinking, she can learn to probe with others (boyfriend or not) so things don't escalate - at least find out what the problem is before you fight and react. There's always time to get mad later, you know.
I'm not saying you can avoid all teen angst but if you show her how to get to the bottom of things, how to express herself, and how to see that others' opinions and rumors about her (if they exist) say a lot more about the other person than they do about her.
Bottom line - neither one of them is very good at relationships yet, so they are both learning. Of course your loyalty is to your daughter, but that doesn't mean the boy made all the mistakes and she made none. You hate it when she cries - of course - but that doesn't mean HE did it all. Some of it is her still-immature way of dealing with the world. On the plus side she is maturing and having greater depth of feeling. That's part of maturing. Any guidance you give her now will really help her when she is on her own.
Again, be thrilled that she is coming to you. She won't always. This is a golden opportunity for you.
Think of teaching a kid to drive - they make mistakes but they get better with practice. You don't reject your daughter, or her boyfriend, because they can't drive on the right side of the road or parallel park on the first or second or third go-round.