Best friend suddenly decided to avoid you... What the heck?

Well, it's possible that your friend might be going through some things. It's also possible that you could've been spending too much time together. Either way, I say you should try to talk to her and see what's going on. If she simply doesn't want to hang out with you anymore, then you must respect her decision and leave her alone. I hope thing go well.

General Advice: With friendship it isn't always about spending every second together. Me and my best friend we almost never talk but when we do its like we never stopped (we've known each other a whopping 20 years). More Specific stuff: I'll ask a couple questions to clear things up Do you two have things in common (still)? Have either one or both of you entered into a relationship? Have you two interacted much if at all in the three weeks since she broke the whole drifting apart / you're boring thing? One thing is also there are some things you can't conquer with sheer effort and willpower alone (of putting yourself out there constantly offering activities etc). It is possible that she just has morphed into a different person just by living and you might not be as an appealing time spent as you used to be (this is rough but isn't necessarily (all) your fault). If you've been trying really hard lately to spend time you might be "imposing" yourself on her (depending on how often you two normally interact with each other) So your overzealous effort might be "what you're doing wrong" like the above said you might just have to fall back and save the battle for another day.