Sorry man, that licks nasty balls.
Though I will admit I did the same thing (not sure if he liked me as much as you liked your gal BUT...) my story was met bob and jim at the same time... got drunk ended up hooking up with bob and we started our booty call, dating, flirting, seeing eachother- whatever you want to call it thing for a few weeks. I was also befriending Jim. I started to like Jim quite a bit more... eventually I decided I liked Jim enough to say peace out to Bob. I did this via text in much the same way your gal did. Have no clue how he felt about that but whatever. I had to let him go, I knew he wasn't the one I wanted to continue seeing, and wanted also to tell him ASAP.
I guess that doesn't help with you pain but yeah... sorry man. Head up time heals all pain