Thanks for your question.
Unfortunately in this case there is no true or correct answer, as I can’t read your friend’s mind… However, it is obvious that your best friend is not indifferent towards you. There are people who like close affectionate physical contact – but that doesn’t necessarily imply anything sexual. Perhaps her knowing that you are bi makes her more comfortable with you being closer physically – but it also entails the possibility that she might not be as straight as she says. Keep in mind that sexuality is a wide spectrum and at times it’s difficult to pinpoint exactly where people stand.
There is a sure way of knowing– and that is to bring the issue up. It is scary and far from easy to do, but if she is truly your best friend, she will understand. You will know inside you when you are ready and when the right moment is to bring it up. Staying in that confused state will not help the case, as you will keep receiving all of her gestures as mixed signals, and I don’t think it’s fair to you – or either of you – and your friendship. Someone might get hurt in the process.
Cheers and hope this will help untangle a few things,