What part wasn't working for you? Is she stuck in your head because you're not one who likes the solitude? Or is she stuck in your head because she was someone you really cares about n loved?

It takes time. You will have memories of her because you were together. You wanted the relationship to work and it didn't. Just let the thoughts be there and let them move on. Don't get with someone new until you are ready and available. Keep yourself busy with things you enjoy.

I agree with tigerdrop. We get used to things, like a habit, and it's natural to have someone or something we are used to stuck in our head for awhile. It helps to fill your head with other things and people. All Tigerdrop's suggestions are good ones, and you can probably think of more.

I m sorry for your break up :-(
I have a hard time letting go of people that are important to me..
Hope you will feel better soon!!!
I usually get involved with helping other people to make my time useful... Or take up hobbies I never had time for.

Exercise, exercise and exercise. That's how I dealt with it.

I am curious why she is still in your head.

My guess would be it wasn't her he wanted. He is lonely and wants a relationship. In my opinion, we idolize what we wish we had and remember the good in someone. Just a guess.

the biggest favour you can do for yourself is learn to be happy alone

it increases your chances of being happy with someone else

Ive had the same problem a few times myself. I call it residue. It does take time for it to slow and stop especially if it was a long term relationship. Things can spark a memory...like living with a ghost of the past. Its good to keep busy. Do things you enjoy. Hang with family or friends. There must have been a reason that you broke up with her so just try to move on. Takes time.,

People we have cared about and shared our lives with do not just evaporate from our minds, it takes time which can really really suck but other than time and distance from the relationship there isn't too much we can do. Keeping busy helps, when you have thoughts of the person make yourself move on to something else because dwelling on thoughts of them can take over very easily. Phone a friend, google something stupid, watch funny videos on YouTube anything that gets your mind on something else. I have found some buzz are stuff on the Internet- just pick any two words and google them! Lol

Exercise, exercise and, oh yeah...more exercise.

When you find something (like exercise) that produces the same kind of feel-good endorphins and pleasure, you'll forget all about her, believe me.