Should I say something or just back off?

Well, my best friend and I have been friends for about 5 or 6 years. Lately, I feel like we're growing apart...and not by my choice. When we hang out I feel like things are fine, but our hanging out seems to be getting farther apart. I know it seems often, but we used to hang out 2 or 3 times a week in the evenings and had lunch a few times a week too. Now, we've been hanging out once a week and I feel like it's by my invitation only. I'm so afraid of growing apart from her because she's helped me through so many extremely difficult times. I even lived with her family for a while when my parents got a divorce and I had no where to go. We went on vacation together and I feel closer to her than I do with any of my family. It's so frustrating because I don't want to come off as needy, but I do need her. I'm worried that if I ask why we've been hanging out less she'll become annoyed because we don't talk about that sort of thing often. Should I just give her some space and see what happens or should I tr to talk to her about what's been going on? :(