I constantly tease my girlfriend, then I flip and become all affectionate before teasing her after a while again. Sometimes we literally play like children except with less clothes on, it's super fun. When we're together we also find some activity to do together. Sometimes we play a game on the Xbox together, we often go out eating, go visit some friends together and some days we just stay home intimately cuddling. Recently we went to the local pool, they have saunas, jacuzzis, playing pools and really hot water baths. We play around in the water, relax, cuddle and then go home super horny ready to fvck.
Another aspect is that we very very rarely communicate on phone or text unless it's for planning something for next time. We both spend time doing things apart from each other, we get the time to think of each other and something to talk about when together. I would grow sick of being with her at all times. I saw her yesterday and I'm not seeing her again until Monday, I'm going snowboarding at a cabin with some friends. I can see her at any time, but I can't snowboard with my friends at any time.
As fastlife says, create and maintain space. It will not only work for her, it will probably also make you genuinely desire to see her and be with her. When you are with her give your entire attention to it, when you are not give your attention to other things and yourself.
My girlfriend doesn't exactly chase me, I wouldn't want her to do that anyways. She knows I'll get back to her, if she was unsure she would just annoy me while I was doing other stuff. It's a trust and respect thing, we respect each others alone time and individual lives while trusting we'll get together for more. Right now this is easy because she doesn't live with me. She's going to move in, but I know I won't constantly stay home pandering to her. I would go crazy if I did and so would she and we both are very aware of that trap. In a way were both working to keep attraction up and seducing each other, I'm turned on like crazy every time I see her and so is she.
She is a source of happiness, but not the only one. I have my friends, my parents, my job and all the other things I really enjoy doing. I know I could do without her, but I'm not turning down a good bonus addition to my life.
So space and time will help, it solves a lot of problems and prevent them from ever occurring if maintained. You get time to think of what you want to do for next time, when that time comes you're super ready and is almost guaranteed to nail having a good time. Only your imagination sets the limit, there's a sh!tload of fun things out there to do.
The mystery that keeps her attracted to you is the same mystery that keeps you attracted to her, it's simple. To create mystery on both parts just get away for a little while, just a few days to half a week to wonder about her.
I know this answer was long, but I hope it adequately answers your questions.