Relationships are complicated and emotions even more complicated. They are mid 20's, the average person in their mid 20's doesn't know shit about what they actually want in life or a relationship. Some luck into a person who is just right, some end up in horrible relationships, some just outgrow the other person as their goals change, some have baggage that ends a relationship, some just stay in a relationship because they are too scared to leave even when the relationship is dysfunctional and some relationships just don't work because one or both are have just not had enough life experience.Meh and if he did leave her alone, she'd bitch about it too.
Also kinds irks me that she acted so hurt about the breakup but she's the one who threw it all away for a shit reason.