IMO, she wanted people to know that she was pretty drunk that night. Instead of just saying, "Yeah, I'd had some wine, but not so much I was out of it," she admitted to drinking a lot of wine and being drunk. She also pointed out how she always goes to bed when she's had enough to drink (and that people could vouch for it), and pointed out that being drunk doesn't change the person that you are.
So whether she was or wasn't drunk, she wanted people to know these things for some reason. We don't have any way to know what the truth is, but we could all make a case for it either way, and a case for it relating to guilt or not. So it's kind of a circular thing to discuss since we don't have a factual starting point. If she does have drinking issues, hopefully Dr. Phil can get her some help.
We need to keep in mind that none of us are the bad guys here. Whatever our opinions are, we all want the same thing - either for Lisa to come home unhurt or, failing that, justice for her precious little soul.