No. People aren't obligated to respond to every text or e-mail they receive during their busy days. Some do, and some don't. You have no idea what she was experiencing when you sent that message. Maybe, she was suffering from horrible menstrual cramps. Maybe, her boyfriend was breaking up with her. Maybe, she was dealing with a crisis at work.
Our relationships can get so screwed up when we rely too heavily on impersonal ways of communication like texts and e-mails. If this friend means anything to you, you'll discuss the matter with her face-to-face and hash it out. You can start by saying: “I was hurt when I texted 'I need a friend' and I didn't hear anything from you.” Then let her explain. Have a conversation.
We shouldn't be so willing to end a friendship based on just one episode. It should be because there's a long-time pattern of negative behavior. If this friend of yours, for example, is consistently unavailable when you reach out for help, then that's a good indication that the relationship isn't working, and it's rather pointless to keep pretending.