This will require some effort on your part, but it's doable
First, you need to stop conveying your neediness. It sounds like you're the one who needs it, and she's the provider. This can put her in a position where she's having sex because of obligation or because YOU want it (not because she wants it).
Second, the next time you do have sex, make sure that you give her an amazing experience. Focus on her pleasure first. In other words, she should be the one having a better sexual experience than you!
Lastly...after giving her a few amazing sexual experiences with you, stop. Meaning, don't initiate sex. Let her do it! You may need to do some flirting etc. to get the ball rolling, but the idea is you become the provider of (great) sex, and she comes to you.
The reason why you want to do this is to make her 'want' something. And in general, people want things that make them feel great.
Good luck