It seems kind of weird that she is asking your friend if something is wrong/you might be depressed again. As in, if she remembered what happened that night I don’t think she would be asking other people why you are being distant. If she remembered doing that I feel she would be the one being more distant and ashamed of herself. Maybe even going a little crazy with keeping her emotions in. I have blacked out a lot in my youth and the number of drinks doesn’t define it. If she was out in the sun all day at a winery she could have been dehydrated then the next drink at the club could have blacked her out. Also, other people don’t know when you are blacked out every time. Half the time people didn’t know I was blacked out, but I sure was. I think you should just talk to her and confront her. I dk what would be worse though, her knowingly and choosing to do that or her being black out drunk/on something and taking part in something she wouldn’t ever chose to take part in normally. Both situations are fucked for everyone.