She just loves you to pieces and is really comfy with you- like a sibling or mother or someone very close- and when she gets really happy and a bit carried away, she bites! Several of mine will do that- purring a mile a minute, all the while-- and NEVER a hard bite, just a little chomp in a playful way-- she's just very fond of you and very comfortable with you- be flattered! (Unless you're spending too much on band-aids, then I'd try and discourage her a bit when she does it.)