I'll give you some advice: Forget about her. I understand she's still in your daily life, but you've gotta move on. It might be hard, but you've gotta accept the fact that the relationship with your EX is over. The relationship ended for a reason. She's called your EX for a reason because it's in the PAST. Now, let it be in the past and move on with your life.
Start working out and improving yourself, do things to make your life more enjoyable and fun. Do anything that'll benefit you and take your mind off of your ex. Read the DJ bible, it's all the way at the bottom of the page.
Also, make sure you're talking to different girls. If you had 10 girls on your phone constantly texting you, I don't think you'd even have the time of day to be worrying about your EX.
Yes, it's probably going to hurt to see your ex with somebody else, but would you rather be sad TEMPORARILY and eventually get over it, or KEEP hurting yourself by staying with your ex. Hell, she probably already has guys lined up to talk to her now that you're out of the picture and you just don't know about it.
My friend, take a long time to think about your own happiness. This girl is nothing to you, nothing but one girl in your long journey of life. Try to make yourself happy and just get your mind off this girl. Getting back with your ex almost never ends up in a good way. Just let her go, and start making yourself happier in life. Find another girl and just keep moving forward in life.