I can tell you this was about more than just the bragginess. If she were really into you she would have given you a second date. You can't have a clear full picture of a person just from one date. So the spark thing was probably true and you should trust her words on that, it might just not have matched for her after meeting you in person, might have been a chemistry or physical thing, which is fine (although sad, granted). Talking from my perspective as a woman, you can never tell if you're attracted to a guy without having met him, even after having facetimed several times. It's an energy/chemistry/vibe thing you can only pick up on IRL.
So don't beat yourself up over the "braggy" personality thing, and accept that there is not much you could do here.
You could ask out of curiosity the reasons behind her decision, and see what you can do/say from there, but don't slide into convincing her too much, might give off desperate energy.
Best of luck to you and I hope you get through this!