Goddess Gabriella realized that this guy was trying to bed her using falsehoods and she got pissed at him. She did not want him to continue doing that and that is why she had to slap the crap out of him for him to learn that those things would not be condoned by the mistress. The pain that the guy felt taught him what the mistress wanted him to learn.
Goddess Gabriella is just not attracted to older guys the way her friends are. But a lot of older guys are attracted to her and she did not know why. She always told them off and they always left her alone. But these two guys did not want to leave her alone and so she had to punish them. She did this by faceslapping them as hard as she could.