I really like some of the other replies to this post.  You may want to consider putting less serious labels on ALL your relationships and friendships.  Let me try to explain briefly.  You mention that your life is "going downhill" when in fact you have merely had an opportunity to see with greater clarity the transient nature of this girl's affections.  Remember the phrase "this too will pass" applies not just to the bad times but also the good times, the fact that things change is most likely not a sign of a downward trend but more likely merely the most recent chapter of alternating good times and harder times, in the future hopefuly you will be taken less off-guard by the inevitable changes and thus you can appreciate the good times more fully.  If she wants to go on a date that does not automatically mean you cannot see other people, if you believe she is with you for the wrong reasons you need not pretend your connection is more serious or exclusive than it actually is.  If you do see her again, I would recommend, as an experiment, paying close attention to how you are feeling in response to her behavior.  She should put forth effort and sensitity to ensure that you feel built up, not torn down.  I suspect that this recent big problem is part of a pattern, usually stupid behavior like that does not occur in complete isolation but rather is part of a bigger picture of a melodramatic cycle that you may be choosing to overlook out of fear of losing the hope that she will fulfill some unrealistic fantasy you may harbor that she is someone that she's not.  Make sure you decide the seriousness of your relationship with her based on who she actually is, not who you hope she is, and remember to keep space in your schedule for people who build you up whether or not it is your ex gf who henceforth I will call by her new nickname "fickle-face".  Hope this helps, I typed it on a phone!!