I agree that you should give her a try. She might just have a certain persona in the waiting room that is very different from in her office (or just a RBF). As an example, the T I saw as a backup when my T was on vacation earlier this year, when I'd seen her in the hallway, she didn't smile or anything. But in session, she seemed more warm and even teared up at a few things I shared with her. So I wouldn't go by that. And I think it's fine to talk about your T's absence with her. When I've seen T's while my T is away, I've often talked about stuff involving him with them, whether missing him, some issues that have come up in working with him, etc. It can help to have another perspective, even just someone to listen.