You know what? I'm sick of you guys! Yes, she's a bestie. What's wrong with that, huh? Is there anything wrong with being a good friend?
Amy is the type of nice gal who will let Sonic and Sally go on a date uninterrupted. She's not petty or jealous or anything like that. She's mature, independent, and knows what she wants, but that's a bad thing, apparently.
So yeah, she's a bestie, and she's the best bestie there is!