You would honestly have to be blind to miss that look. Haruka caught the waiter's attention once she was sure Michiru was out of earshot, quickly arranging for him to bring her one of those cheesecakes once she came back from her... refreshing herself, or whatever she wanted to call it.
In the meantime, she could at least wonder what the hell she'd meant about 'learning a thing or two' from her. How could she do that? She... wasn't going to try and make her ladylike, was she?