An issue with training and heat

So. My 7mo Bernese is in heat, at the stage where she's stopped bleeding but she's still fertile. She's been a lot more cuddly and generally velcro-like, and a lot more reactive to things she's scared of (like the vacuum cleaner) which in general is within what I expected. As background, she's been training since 3-4mo, and we go to a nearby mall once a week, which she likes. All is good there.

Today, however, she was particularly odd. We didn't run into any other dogs, and she handles people well by now. We were sitting down on a bench, as we usually do, and she lays down so we can just people-watch. Trainer then excuses himself to the bathroom. Immediately she's up, definitely stressed, refusing both treats and commands and generally looking towards the way to the bathroom. It was strange, but she was fine with some pets. I didn't mention it, and it wasn't an issue the rest of the session.

Now. Trainer leaves, and it's pandemonium. She TUGS towards the door (and this is a 60lb dog atp, which THANKFULLY I can handle, but it's not by any means easy), refuses to go back with me and if I tried leading her wherever she didn't want to, she'd sit and refuse to move. This has NEVER happened in any session before, by this time she is usually tired and satisfied with the walk and is very compliant with driving home. She's never outright refused my commands in this context.

I'm puzzled. The only thing that changed between this session and all others is that she is in heat, and while she's familiar with him, she sees this man twice a week at most. Is this… normal?