Honestly, why can't the dog just be crate trained properly? And also, if guests are over, you should be mindful of the dog. If you are in the kitchen cooking and not watching the dog, bring the dog in the kitchen with you and babygate her in with you while you are cooking or something.
Another thing to consider - have her eyes been checked. 8 is an "older dog" for a lab and not seeing as well as she used to and then suddenly someone gets up, etc, could be something provoking because she can't see too well. Ditto hearing.