If you feel like the spark in your relationship is gone, then it may be better to end what you have. Maybe you can start by asking her for some space and explain it properly and tell her that you need time to find yourself or that you want to think things through because you have a lot on your mind.
If you don’t miss her during the time she’s not in your life then that’s a clear sign that you should go ahead and fully break up with her. Yes, she will get hurt but that’s better than continuing the relationship when you no longer have feelings for her.
She may feel the pain at first but she will eventually move on and meet someone who is truly compatible with her.