Cringing harder than feeling sympathy. Girls always do whats most emotionally exciting not whats most healthy for them as people. It was probably emotionally healthier for her to seek your companionship but she chose to entertain going back to her relationship because there is history there. Honestly the fact that she still texts and calls her ex means that she wasn't ready to move on and first place and you deserved better she was just using you to fill a void she wasn't actually interested in who you are as a person. It happens to the best of us. This is why I always tell girls dating girls isn't going to solve their problems you'll just be dealing with girls the same way that men are dealing with them and it's probably just going to serve to make their dynamics with women just as complicated as their dynamics with men. LDRs rarely work. Most end in the person just ghosting.