Gotta love shoujo xD The story wouldn't be complete without one of these moments.
I'm sure it's going to work out. I can't see Yoh having a field day about it. Maybe initially, but I doubt it. Haruna was surprised herself.
And the glasses chick is just trying to stir the pot. It sucks because if they had gone on the date, Haruna would have had no problem; she would have completely forgotten it. (Whereas some would have thought about it constantly during the date). She knows she's being unreasonable, but she can't help it.
But, of course, I'm sure it's gonna work out ^^