Is she really my bestfriend?

I've know this girl for about a year and we use to always talk and she trusted me alot and we helped each other with alot of problems. (depression) but lately she never responds to her texts and when she finally does she says she's been busy. She still says I'm her bestfriend and she even told my friend that. But it's really hard for a dude like me to understand why the **** she's being like this. Do you think she's really my bestfrind like she says she is? I need an answer from a girls point of view cuz as a guy I'm way lost about all this