I am guessing the person who told you that she won't ever be your best friend has a different idea of what that means than you do. Please don't let it discourage you from trying. I think you are an incredibly kind person. Of course you can let her try your assistive communication, and try other things, but maybe all she wants is for her to be herself around you too.

Why did you say she should not be forced to use it? Are you going to be forced to use it? Do they force either of you to do other things?